INCANDESCENT 
ELECTRIC 
LIGHTS 
With 
Particular reference 

to the 
Edison lamps at the 
Paris Exposition, 

By < 
Th. du Moncel 
and 
Wm. Henry Preece. 



New York 
D. Van Nostrand 
1883 




<£* 






INCANDESCENT 

LECTRIC LAMP; 

AT THE 

international Exhibition of Electricity. 

BY 

COMPTETH. DU MONCEL, 



m ki La Lumiere Electrique? 



c. 4-JLJL 



/ 1 



PREFACE. s 

1 
the successful experiments of s 

in maintaining a steady light of 
ansityhave become widely known, 
' n ^ber of systems have been 
it forward by different inventors, 
iblio interest in the growth of 
nventions affords a sufficient ex- 
f the appearance of an essay 
.present. The relative value of 
ystems of lighting for interiors, 
specially to economy of outfit 
ni power to maintain, will 
attention of all resi- 

^w by Comptedu 
international 

ays, re- 

i 

£ERIX(t 



IV 



gazine, one on "Economy of Electrj 
; ghting," by Mr. Howell, of Steven 
stitute, and another on " The Dynarac 
ectric Current," by Dr. C. Willian 
smens, and a third by W. H. Preec^ 
I the results of the Paris Exhibition. 



len^' 

jhCANDESCEHT electric lamps. 



•ISON S SYSTEM OF ELECTRIC LIGHTING. 

'he incandescent system was first rep- 
uted by lamps made from an mean - 
•ent jDlatinuni wire, and the interest- 
i experiments made in 1879 by M. de 
| pigy, should be recollected ; but the 
! -Actical workings of this system were not 
;atisfactory, principally because of thedis- 
iggrer ation and partial fusion of the wires, 
md n> spite of the numerous improye- 
ne ) brought to bear on this system by 
iison, who, by one of the most in- 
; of processes, had rendered them 
r fusible and harder, still they had 
absolutely rejected — at least for or- 
• , ""i.'iiips. Then it was suggested to 
oy carbon which, if not allowed to 
, is infusible it the highest heat de- 
)ed in the hrnps, and different ar- 
ements of apparatus were put to- 
) at various times by King, Lody- 
5 Bouliguin«, Swan, Sawyer, etc., 



some avoiding combustion( 

the lamps in receptacles where » 

had been obtained, others by fillin^ 

receptacles with gases unfit for coml^ \ 

tion. as nytrogen or oxide of carbon, 1 .1 

simply by leaving the air shut up in ij 

receptacle to be vitiated by an incipij 

combustion. 

ini 1 
All these attempts had but part 

succeeded, to say nothing more, w; ian | 
in 1879, the new incandescent carlc< 
lamp of Mr. Edison was announced, an 
many savants, and myself in particula: 
doubted the exactness of the allegation 
which came to us from America. Th 
carbonized paper horse shoe appeared] 
incapable of resisting mechanical shocks 
and of supporting incandescence for 3 nv 
length of time. At this epoch Mr. § wan 
himself said that up to that time he 
had not been able to o^feiii any very 
satisfactory results by an analagous dis- 
position ^>f the incandescent organ. 

Mr. E tson, however, was not abashed 
and in spite of the lively opposition made 
to his lamp**, in spit) of the bitter po 



lemic of which he was the object, he did 
not cease to perfect it for practical pur- 
poses, and has at last produced lamps, 
which we have seen at the Exposition, 
and which can be admired by all the 
world for their perfect steadiness. These 
lamps, to the number of 160, light the 
two salons reserved for the discoveries 
of the ingenious American inventor, and 
we shall see still more important results 
upon the installation of the great ma- 
chine which is expected from America. 

As at present made, these lamps are 
sufficiently solid and can last a long time. 
The originally fragile carbon has become 
extremely elastic and hard, an:l of such 
attenuation that it can be well compared 
in size to a horse hair. By a cleverly 
combined system of fastening the plati- 
num, conducting wires are not exposed 
to be cut, and they are so sealed in the 
glass receiver that their change of vol- 
ume under the action of hea' does not 
endanger the perfection of tJ vacuum. 
By the way the carbons are treated when 
the vacuum is made in the globe, the 



10 

bubbles of air enclosed in their pores 
and which, in escaping, disaggregate the 
surface, are evacuated before closing the 
lamp, and at the same time the filament 
of carbon acquires a peculiar density and 
hardness, as was the case with the plati- 
num wires. To obtain this result the 
carbonized filament must be brought into 
incandescense while the vacuum is being 
made. The very nature of the substance 
of vegetable origin employed in its 
fabrication, has been modified. 

Fibers of bamboo are now used instead 
of the paper originally employed. These 
are carbonized by a certain process, and 
the successive transformation of these 
fibers into carbon filaments may be fol- 
lowed in several collections to be seen at 
Mr. Edison's exposition, and which will 
gratify the curious, and are worthy of 
study. According to Mr. Batchelor and 
Mr. O. A. Moses, co-laborers of Mr. Edi- 
son, and who represent him at the expo- 
sition, the resistance of these filaments 
is 125 ohm, when brought up to an in- 
candescence corresponding to 16 candles ; 






11 



but it can vary according to the luminous 
power desired of the lamps, for it can be 
distributed between two lamps, whose 
filaments are correspondingly more or 





Fig. I. Fig. 2. 

less long. Their extremities, which are 
enlarged, are pressed in a kind of pincer 
which terminates the platinum conduct- 
ors, and which are soldered by an elec- 
trolytically deposited copper. Figs. 1, 2, 3 



12 



and 4 represents the actual arrangement 
of these lamps. Their duration, from what 
I have been assured, is long enough ; 




Fig. 3. 

however, they must wear out. Although 
most of them may have served for 1,200 
hours, the question may be askedjwhether 
a lamp capable of deterioration may be 



13 



considered a practical thing ; but if it is 
considered that this lamp can be fur- 
nished for 30 cents, that the adjustment 




on its support cannot be any simpler than 
it is. which is evident on inspection, it is 
easily seen there is no more trouble to 



u 



replace one than to renew a broken lamp 
shade. 

What constitutes Mr. Edison's system 
is not alone his lamps, it is the totality of 
the arragements referring to them and 
which have attained such a degree of 
simplicity that henceforth nothing re- 
mains to be desired in practice. Gene- 
rating machines, distribution of circuits, 
installation, indicating and regulating 
apparatus, meters for measuring the 
amount of current employed are all com- 
bined for immediate application. As 
we have said, this application is about 
being made in a part of the city of New 
York, where a great number of houses 
are to be lighted by this system, by 
means of a subterranean distribution 
from a central station, from which also 
motive power will be distributed to the 
houses. 

This central station will be provided 
with twelve steam engines of 150 horse 
power each, actuating dynamo -electric 
machines, each of which will be capable 
to supply, it is said, 2,400 lamps of 8 



15 

candle power. The current furnished 
to these lamps comes through a branch 
taken before each house from the large - 
sized conductors laid in the streets. 
These deviations bring the poles of the 
generator into each house, where the 
lamp wires can be brought in connection 
with them, thus rendering each house 
independent of any other, both for a 
supply of light and motive power. 

When it is considered that the system 
of distribution adopted by Mr. Edison, 
the total resistance of the exterior cir- 
cuit is extremely reduced and that with 

64 
2,400 lamps it is only , say, about 

.026 of an ohm, it can be seen that a very 
feeble resistance should be given to the 
generating machine ; so that its first ar- 
rangement has been modified. To begin 
with: The field magnets were arranged on 
a derivation taken from the commutator, 
putting it into the induced circuit as in 
"Wheatstone's and Siemens' system. 
Then the armature was arranged on Sie- 
mens' principle, so that the wire con- 



16 

sisted of bars of copper. These bars 
lie close to each other around the cylin- 
der which forms the armature, and they 
generate the current. Their extremities 
correspond to discs of copper (at right 
angles to them) laid one against the other 
at the ends of the cylinder, and insulated 
from each other. Each bar is fastened 
to its corresponding discs in such a way 
as to form a single circuit enveloping the 
cylinder longitudinally, and which is 
made perfect through the coupled bars 
two and two with the commutator blocks 
(made after the Grammes pattern). Figs. 
5 and 6 give an idea of this new 
arrangement. The center of the cylin- 
der itself is occupied outside of the ro- 
tating axle by a cylinder of wood, which, 
in its turn, is surrounded by a thick tube 
made of a series of very thin discs of 
iron, separated from each other by tissue 
paper. This arrangement facilitates the 
rapid changes of polarity in the plates. 
This tube is terminated at its two ex- 
tremities by two thick clamping discs 
which are made to compress the others 



17 

laterally, and the copper discs of the 
working coil occupy the two compart- 




Fig.5. 

nients at the extremities of the cylinder, 
as seen in Fig. 5. Under such condi- 
tions as these the resistance of the gene- 



18 



rator is small, and permits of great sub- 
division of the current in multiple arc ; 



Fig. 6. 

nor is there any insulation to be burned, 
and it is even possible, in case of the 
deterioration of the bars, to renew them 



19 

easily, for they are simply screwed against 
the copper discs corresponding to them. 
Jn the new disposition adopted by Mr. 
Edison, the field magnets lie horizontal 
instead of being placed in the vertical. 

Fig. 7 represents the whole machine as 
now actually working in the Palais de 
l'lndustrie. 

We have described the generating ma- 
chine before completing the description 
of the system of distribution of the 
current, because we ought to speak 
of the system of control used in 
making the current uniform when its in- 
tensity has been modified by a variation 
in its distribution ; that is to say, follow- 
ing after a variation resulting from the 
unexpected suppression of a certain num- 
ber of lamps in a part of the system. 
The necessities of this system are easily 
understood, if we consider that this sup- 
pression can lead to a greater or less in- 
crease in the intensity of the current 
feeding the remaining lamps. 

In France several systems have been 
devised to obtain an automatic regula- 



20 



tion, but in America, it seems, it is pre- 
ferred to effect this by the intermediation 
of an appropriate controlling agent. 

In this system, in whose general ar- 
rangement we see, in Fig. 8, the current 
which feeds the lamps furnishes a devia- 
tion at the machine cc, which enters an 
electric dynamometer, after having gone 
through a resistance of 180,000 ohms. The 
electro -motive force should be about; 110 
volts, and a difference of one volt should 
correspond on the scale of the indicating 
apparatus to three divisions ; conse- 
quently, for each observed increase of 
intensity a resistance capable of compen- 
sating for it should be introduced into 
the circuit. Mr. Edison has established 
a circular commutator e with bobbins of 
different resistance, which permits of an 
increase of resistance, not in the lamp 
circuit, which would lead to a loss of 
work, but in the circuit of field magnets, 
which weakens their action on the work- 
ing coil. From the central station also, 
the condition of the current affecting 
the lamps can be controlled by means of 



3 <o *r- 5 % 



21 



5_ i* 

^1L|^ 



o 



o 



r 



>5h 






riS 



o| 



o 






o 



o 



o 






o ^ 



"^ 



ill 






pi 



p - o ; 



Fig. 8. 



22 



a testing photometer, which enables us to 
see how much the intensity of the cur- 
rent must be diminished or increased to 
correspond to a given luminous intensi- 
ty. For this purpose the photometer is 
mounted on a little railroad, placed in a 
dark chamber ; under and in front of it 
is placed a scale, arbitrarily divided, so 
as to indicate immediately the candle 
power furnished by the current in its 
normal condition. The left side of Fig. 8 
indicates the manner of arrangement of 
the testing bench, with the explanatory 
table at the bottom of the figure. Fig. 9 
shows it in perspective. The manner in 
which derivations are taken on the princi- 
pal conductors merits especial mention. 
The conductors are composed of two rods 
of copper of hemi- cylindrical form, flat on 
one side and round on the other, which 
are enveloped in cylinders of insulating 
material, contained in small wrought-iron 
pipes, which are buried under the streets. 
To take a derivation the cable is laid 
bare at the spot where the branch cir- 
cuit is to be established. The two con. 




o 
il 






24 



ducting rods (coming from the main coi 
ductors) are cut and bent outwards ar i 
introduced into a clamp where they ai 




soldered to the house wires, as shown in 
Fig. 10 ; but in order that no harm can be 
done by two strong currents, one of these 
communications is made by intercalating 



25 



a lead wire in the branch circuit, shown 
at the bottom of the figure, and which, 
by its fusion, interrupts the circuit. This 
is what is called in America a "cut off; 1 ' 
and in this way it prevents deterioration. 
The box is then hermetically closed and 
covered with an insulating coating. In 
the figure the branch wires are shown 
double, but it is evident that they could 
b e single. 

We said that all arrangements had 
been made to make the system a perfectly 
practical one, and of that we will soon be 
able to judge. Let us examine first how 
the lamp supports and the lamps them- 
selves are disposed. As has been seen, 
they are formed of glass globes of ovoid 
form, cemented into copper sleeves by 
means of plaster and screwed into cylin- 
drical cavities terminating the supports. 
These are a kind of arm which can be 
adapted to brackets or chandeliers, or be 
arranged around the walls. In the last 
case, the arm, as is shown in Fig 11, carry 
two articulations, A and B, and commuta- 
tions are made by two plates of the hino-es 



26 




27 



which are insulated, and in whose circu- 
lar part two springs press, as seen in 
Figs. 12 and 13. Connections of the con- 




ductors with the lamp, as we have indi- 
cated above, are made by a lead wire (cut 
off) which may melt and interrupt the 



28 



circuit in case a too great quantity of 
current should endanger the lamp. 

In these brackets, as in the three 
branch chandeliers, represented in Fig. 
14, keys have been introduced which 
allow the extinction of the lamps separ- 




Fig. 13. 



ately or together, without causing any 
spark of the point of rupture or any dan- 
ger of fire. The movement of the key a, 
as shown in Fig. 12, breaks the contact by 
means of a. conical stopper which termi- 
nates the screw of the key, and which, 
when separated from the two plates, 
through which the current passes when 
the stopper is in contact with them, 



:29 



breaks the circuits at the points and on 
a surface of sufficient extent to greatly 
diminish the spark at the point of rup- 
ture. 




Fig. 14 



The lighting of the two salons of Mr. 
Edison at the Exposition is done by 16 
small chandeliers like the above, two 
grand crystal chandeliers and 80 brack- 
ets. 



30 



The effect is very beautiful, the steadi- 
ness being as complete as could be de- 
sired, and if, as I have been assured, the 
price of this kind of illumination is lower, 
light for light, than gas, it may be con- 
sidered that the problem is on the eve of 
solution, for Edison's system of electric 
lighting is placed in the same condition 
,as that of gas. He avoids the presence 
of machines in separate houses, which 
always are in the way, and which, by their 
very nature, require care and manage- 
ment not to be obtained from ordinary 
servants. 

As a complement to his system, Mr. 
Edison has constructed portable chande- 
liers, represented in Fig. 15, and a cur- 
rent regulator shown in Figures 16 and 
17, which permits of reducing the light 
in any desired proportion. It is a car- 
bon rheostat, composed of carbon pen- 
cils of different sections, which, as the 
current passes through one or the other, 
allows any desired intensity. The appa- 
ratus is enveloped in a cylindrical cover, 
pierced with holes to allow of the escape 



31 



of heat, and surmounted by a lamp 
which indicates to the eye the desired de- 
gree of luminacy. It is worked by a 



*£* 




Fig. 15. 




Fig. 16. 



disc, shown separated in the lower part 
of Fig. 16, and which can be turned so 
as to bring a contact spring on any one 



32 



of the supports of the carbon, whose 
position is indicated by an index and di- 
visions engraved ^n the base of the 
cylinder. 




F!g. 17. 

But what is most interesting of all in 
those accessories of Mr. Edison's sys- 
tem, is the meter which determines the 
amount of electricity consumed by the 



33 

lamps. There are two kinds, one auto- 
matic like a gas meter, the other requires 
weighing. They are, however, both 
founded on the same principle, that is to 
say, in the estimation of work by the 
weight of a copper deposit produced by 
the current used. We will describe these 
two interesting pieces of apparatus here- 
after, and give drawings of them; to- 
day we must be content with only men- 
tioning the principle involved. 

Imagine a balance having at the extrem- 
ities of the beam two cylindrically rolled 
plates of copper forming two electrodes. 
Let us admit that these two systems of 
electrodes, which plunge into two vessels 
filled with a solution of sulphate of cop- 
per and furnished with fixed electrodes, 
are traversed in an inverse direction by 
the current employed, and which can 
cause the balance to operate under a 
given weight of copper deposited from 
the solution. It is easily seen that the 
movement brought about by these con- 
ditions can set in motion a current re- 
verser, which can change the conditions 



34 

of the deposits in such a way that the 

ith copper, is tr 
form '.uble elt- while the 

one which vr \ nally in that condi- 

tion iie reducing electrode. 

ime on an oscillating motion 
of the be he balar Polished. 

and man - frequently : I, ac. 

cording to the rapidity rmation 

according to 
the intensity of the current Afi the same 
moY- an bring -sage 

of a ken from the 

tal curre ial electro-mag- 

net, which commands the movement of a 
liter, it ifi fcer the deter- 

mination of the number of Amperes cor- 

onding to the weight 
which produces the oscillation of the 
balance) what is the quantity of elec- 
sramed 
The realization of this idea has ne 

ifi electro-magnetic arrange- 
ments, which we will describe in detail 
when we get the drawings of the appa- 
ratus. 



35 

The other system is more simple, con- 
sisting of two voltameters of sulphate 
of copper, whose electrodes can be easily 
taken out ai)d weighed, as the work done 
can be calculated from the weight of 
copper deposited. One of these voltame- 
ters is open to the subscriber, the other 
is kept closed by the controller. Resist 
ance bobbins introduced into the circuit 
corresponding to these resistance, per- 
mits of the employment of greater or 
less periods of registration. 

A small incandescent lamp placed be- 
neath the apparatus, and which can be 
thrown into circuit by a simple metallic 
thermometer, prevents any danger of 
freezing in extremely cold weather. 

There is another application of Mr. 
Edison's light, which can be seen at his 
exposition in a model intended for light- 
ing galleries in mines. In this arrange- 
ment, represented in Fig. 18, the lamp is 
introduced in a glass receptacle filled 
with water and held in suspension. 
Communication of the apparatus with 
the circuit is arranged in such a way 



36 



that the points of contact are covered by 
water, which avoids any danger of ex- 
plosion in mines infested with fire damp. 




Fig. 18. 

To give an idea of the application of 
Mr. Edison's systems, we have represent- 
ed in the large engraving accompanying 
this article, Fig. 19, the interior of a 



37 

parlor lighted by the small chandeliers 
previously described. As is seen, the 
electric light is projected downward, the 
best arrangement for reading and writ- 
ing. This method seems to be preferred 
by Mr. Edison, but as can be seen above 
described that all styles of illumination 
can be produced with this kind of light, 
analogous to that obtained with candles 
or gas jets, it is simply a matter of 
taste. 

Mr. Edison's lamps are not alone em- 
ployed in the two salons reserved for 
him, they are to be found in various 
places throughout the great nave, nota- 
bly at the exhibits of Messrs. Heilman, 
Ducommun et Stienben (of which we 
gave a drawing in a previous article) 
and at the exhibit of Messrs. Sautter 
and Lemonnier. At these two places 
the currents are furnished by two 
Gramme machines, type A, and each one 
lights about 40 lamps. Now that Mr. Edi- 
son's great machine (a drawing of which 
is shown on frontispiece) has arrived at 
the Exposition, it will be possible to ob- 



38 



tain, with the incandescent system, illu- 
minations of greater magnitude. The 
landing of the great staircase will be lit 
in this way. It is proposed to accom- 
plish this by means of a crystal chande- 
lier of 144 lamps, and of others furnish- 
ed with 25 lamps each, to be hung from 
the different panels, and of girandoles 
standing on the 16 pilasters of the stair- 
case. This will produce an enchanting 
effect and a brilliant illumination. I am 
not quite sure that this mixture of arc 
and incandescent lights is a happy 
thought. It is evident that the latter 
destroy the effect of the former, and 
might lead one to believe that the lumin- 
ous intensity of the incandescent lamp is 
less than it really is. Again, the differ- 
ence in the color of the lights is so con- 
trasted that many persons who reproach 
the electric for its ghastly aspect, find it 
too red in incandescent lamps. It is 
evidently an effect of contrast, for the 
light of incandescent lamps is whiter 
than that of gas jets, which, neverthe- 
less, these same people find very agreea- 



39 

ble. If required, incandescent lamps 
can give a dazzling white just as well as 
the others ; it is only necessary to employ 
a stronger electrical intensity, then they 
lose their peculiar qualities, that of giv- 
ing a soft light which does not fatigue 
the eye and of an easier and more com- 
plete subdivion. 

It is certainly very difficult to satisfy 
everybody, and that many persons hardly 
know what they do want : above all, when 
the effects of contrast momentarily im- 
pair the power of judging correctly. On 
the other hand, there are certain fault- 
finding spirits who are never satisfied 
with anything ; witness the author of that 
incomprehensible article that recently ap- 
peared in a certain journal, who pre- 
tended that only discordant sounds and 
puppet-show voices could be heard in the 
telephones from the opera. The author 
in question who could perpetrate such an 
enormity must have had his ear as sick as 
his humor. The crowd passing every 
evening before the telephone rooms at the 
Exposition, is the best proof of the inanity 



40 



of such judgments, and by this can once 
more be seen the value of the scientific 
lucubrations of certain political journals. 

The same thing happens with the elec- 
tric light, and quite a number of persons 
who, without previous examination, and 
without being of the same opinion two 
days consecutively, come to us and dis- 
parage electric lighting. It is certain 
that new inventions have great difficulty 
in coming to light and in succeeding, 
above all when they are opposed by rival 
interests, but when they are really good 
they triumph in time over all obstacles. 

We would like to give some informa- 
tion about Mr. Edison's new machines, 
but as they are not yet put up we re- 
serve the description for another time ; 
we will only say that the steam engine 
was constructed especially for this appli- 
cation, that it makes no noise, and that 
the dynamo-electric machine forms one 
of its integral parts. The field magnets 
of this latter-mentioned, in place of be- 
ing vertical as in the model represented 
in Fig. 7, is horizontal, and the dimen- 



41 



sions cf the machine itself are much 
larger. 

The steam engine, which works the 
machine, is of peculiar construction, and 
the speed of rotation which is communi- 
cated to the working coil is 350 turns a 
minute. This is not a very great speed, 
but the armature is very heavy, weighing, 
as we are told, over three tons and a half. 
The magnetic field in which it turns is 
formed by three powerful eleetro-mag- 
ets, united so as to form but one at their 
extremities. In the salon of Mr. Edison 
are a collection of photographs, among 
which may be seen some of the manu- 
factures where the enormous amount of 
material required in these installations is 
constructed. As we have been assured, 
one of these turns out 2,000 lamps a 
day, giving occupation to 150 persons. 
In accompanying drawings and collec- 
tions can be seen methods of glass blow- 
ing, the carbonizing of the filaments in- 
tended for incandescence, the vacuum 
pumps and the mounting and packing of 
the lamps. The pumps referred to are 



42 



set in motion by dynamo-electric ma- 
chines. 

From all this, we see Mr. Edison's sys- 
tem to-day is completed, perfectly stud- 
ied out in all its parts, and that nothing- 
more remains to be done, but to intro- 
duce it on a great scale. 

Th. Du Moncel. 



[Note by the Translator.] 
DESCRIPTION OF EDISONS STEAM DYNAMO. 

(See Frontispiece.) 

Peculiar to the Edison system is the 
idea of connecting an engine of great 
power directly to the armature shaft of a 
single dynamo, capable of absorbing the 
full power of the engine, and of econom- 
ically converting the same into electrical 
energy for distribution to the lamps and 
motors. To obtain the requisite electrical 
pressure, and avoid the use of magnets 
and armature of a weight and size which 
for mechanical and commercial reasons 
would be excessive, the engine is so con- 
structed as to maintain a speed of 350 



43 



revolutions. A boiler pressure of 120 
lbs., made absolutely safe by the use of 
approved sectional boilers, the high speed f 
and variable cut-off valve, and manner of 
constructing the engine makes this 
method of generating electricity abso- 
lutely safe and economical, and the uni- 
formity obtained in regulation of speed 
insures a corresponding steadiness in the 
current and therefore in the lights which 
it supplies. 

The following approximate summary 
of weights and dimensions of various 
parts of the latest " steam dynamo " 
constructed will give an idea of its 
total size and power. 

Cast-iron sole plate, in one piece, upon 
which dynamo and engine are placed, 
and pillow blocks, 9,600 lbs.; Magnets, 
complete, 24,500 lbs. ; Armature, com- 
plete, and shaft, 8,500 lbs.; Engine, 
10,000 lbs. Total weight, 44,600 lbs. 

.The total weight of copper on arma- 
ture and magnets is 3,600 lbs. 

Principal dimensions: Sole plate 12£ 
X 8J f t. ; length of magnets, 8 ft. ; 



44 



length of armature (commutator makes 
additional length of 9") 5ft.; diameter of 
armature, 28"; Engine cylinder, 11" X 16"; 
capacity, 2,400 gas jets. 



OF 

Electric Lighting 

BY 

INCANDESCENCE. 



_-. josjr zl. 

Stevens 1 Institute of Technology. 



I. — Economy of the Generator. 
II. — Economy of the Conductor. 
III. — Economy of the Lamps. 



Economy of Electric Lighting 
by Incandescence. 



In writing this thesis I have endeavored 
to determine as nearly as I was able the 
cost of electric lighting by incandescence. 
Owing to the interest attached to the sub- 
ject, and the lack of data upon which 
calculations can be based. I have endea- 
vored to consider the subject in all its de- 
tails, and have taken every precaution that 
suggested itself to guard against error. 

The data given are sufficient to calcu- 
late the number of lamps to be obtained 
from each indicated horse power in a 
steam engine ; beyond this I have not at- 
tempted to go, as my experience is insuf- 
ficient to enable me to make any further 
determinations. 

EFFICIENCY OF THE GENERATOR. 

The generator tested was one of the 
latest pattern devised by Mr. Edison. It 



48 

differs from the generators heretofore in 
general use, principally in the substitution 
of bars of copper for wires in the armature, 
which make the resistance of the armature 
very low and also economizes space, as the 
bars have a trapezoidal section, and when 
in position there is only clearance enough 
to allow for the insulation between them. 
In my experiments the field was excited 
by a current shunted from the main cir- 
cuit, the relative resistances of the mains 
and magnet coils determining the amount 
of energy expended on the magnets, and 
consequently the intensity of the magnet- 
ization and the electro-motive force of 
the generator. 

APPARATUS FOR MEASUREMENT OF THE ME- 
CHANICAL ENERGY TRANSMITTED TO THE 
GENERATOR. 

In measuring the energy transmitted to 
the generator, the dynamometer built by 
the class of '79 was used. This was care- 
fully standardized by supporting the pen- 
dulum in a horizontal position at a point 
2 feet from the axis of the shaft, and 



49 



weighing the pressure of the support upon 
a platform scale ; the weight of the pen- 
dulum and support was 183.25 ; the weight 
of the support was 12.1 ; the weight of the 
pendulum was 171.2 lbs. 

This gives us the force acting at the 
cncumference of a pulley of 1 foot radius 
by multiplying 171.2 by the sine of the 
angle of deflection. This is a measure of 
the force transmitted through the gear at 
the top of the pendulum, and includes, 
beside the force required to turn the arma- 
ture in the field of force, the force neces- 
sary to overcome the friction of the dyna- 
mometer bearing, and also the friction- of 
the armature shaft in its bearings. In 
order to determine what part of the trans- 
mitted energy was lost in overcoming 
friction, a Prony brake was applied 
to the pulley of the .armature, close 
beside the belt, while the generator 
was running. Removing the brushes 
to be sure no current was generated, 
we tightened the brake until the pen- 
dulum showed the same deflection that 
it did during the test : we thus made a 



50 

direct substitution of the Prony brake for 
the retarding action of the lines of mag- 
netic force upon the armature when the 
circuit was closed, and the force exerted 
by the arm of the brake, upon a platform 
scale reduced to the radius of the pulley, 
will be the force required to turn the 
armature in the field of force. Instead of 
measuring the pressure exerted by one arm 
of the brake upon a scale, we measured 
the lifting effort exerted by the other end 
upon a weight resting upon the scale. We 
placed a light counterweight upon the 
other end of the brake, to make the zero 
reading more definite, and in getting the 
zero we raised the counterweighted end, 
and let it down gently, rapping the 
center of the brake to prevent sticking. 

Several readings fixed the zero between 
35 | and 35. Running at about the same 
speed as in the test, and tightening the 
brake until we got a deflection of 42°, we 
made several readings on the scale, which 
varied from 19 to 20^. Using the highest 
zero reading and the lowest running read- 
ing, we get a force of 16J lbs. acting at a 



51 

distance of 2 feet from the center of the 
shaft ; this reduced to the radius of the 

24 

armature pulley gives 16 J X —=79.2 for 

o 

the force acting at the circumf erence of the 
armature pulley. If no friction had inter- 
vened this force would have been 

171.2 x (sine 42° = 66.913) ft - . „ 
To* =91.644 lbs., 

showing a loss of 91.644—79.2 = 12.444 
lbs., or 13^ per cent, of the power trans- 
mitted. 

This loss of 13 J per cent, is caused by 
the friction of the dynamometer and the 
friction of the armature bearings. To get 
the force actually applied at the circum- 
ference of the pulley on the armature 
shaft, we must determine the friction of 
the dynamometer bearing alone. To do 
this we made a wooden brake of the same 
diameter as the chiving pulley on the 
dynamometer that could run on a 10-inch 
pulley on the dynamometer shaft, we then 
clamped the Prony brake upon the dynamo 
pulley, and also clamped the belt on the 
dynamo pulley and passed it over the 



52 

wooden brake. Running under these con- 
ditions and tightening the wooden brake 
on the 10-inch pulley until the pendulum 
showed a deflection of 42°, we measured 
the force acting at the circumference of 
the dynamo pulley and also at the circiun- 
ference of the dynamometer pulley by the 
lifting effort of the Prony brake upon the 
weight on the scale. The object of this 
arrangement of brakes was to get the 
friction under the same conditions as 
those under which we ran the test. To 
get the zero reading in this case we 
clamped the Prony on the dynamo pulley, 
and loosened the wooden brake and coun- 
terweio'hted the other ami of the Pronv 
brake, until the armature turned in its 
bearings ; then letting it come to rest and 
rapping the bearings of the dynamo and 
dynamometer, we determined the zero 
reading to be 33 lbs. Several readings 
fixed the readings for -42° at 16 lbs., 
therefore the force acting at the circum- 
ference of the dynamo pulley was (33 — 16) 

- 24 

A —=81.6, showing a loss of 91.644—81.6 
5 



53 

= 10.044 lbs., or 10.9 per cent, of the 
total energy transmitted. 

APPARATUS FOR THE MEASUREMENT OF 
ELECTRICAL ENERGY. 

The resistance over which the gen- 
erator worked consisted of three strands 
of iron wire in multiple arc, each of which 
was .104" in diameter. These were 
stretched from one gallery of the shop 
to the other in the open air. 

In measuring the resistance of the dif- 
ferent parts of the circuit wires were led 
from the binding posts of the generator to 
the Wheatstone bridge, then by breaking 
the connection with the armature and 
magnet coils, we could measure the re- 
sistance of the line, or by breaking the 
connections with the line and magnets we 
could measure the resistance of the arma- 
ture and leaders, or by breaking the con- 
nections with the armature and the line we 
could measure the resistance of the mag- 
net coils. 

The electrical energy developed in the 
circuit was determined by three methods : 



54 



1st. By a voltameter, or a copper-de- 
positing cell. 

2d. By a calorimeter. 

3d. By measuring the electro-motive 
force and resistance. 

FIRST METHOD. 

The voltameter consisted of a glass jar 
large enough to hold six plates of copper, 
7"x8". 

These were placed h" apart, and held 
. in place by a light wooden frame. They 
were connected alternately to the positive 
and negative wires from the generator. 
This method of arranging the plates brings 
both sides into action, gives a large area 
of plate, and makes the resistance of the 
cell very low and the consequent heating 
very little. By means of mercury con- 
nections the voltameter could be thrown 
into or out of circuit instantly without 
breaking the current, and the leaders w T ere 
so proportioned that throwing it in and 
out did not alter the resistance of the cir- 
cuit. 

In calculating the current from the 



weight of copper carried from one set of 
plates to the other, the weight gained by 
the negative plates was considered as the 
weight carried over, and the constant 
.32456, given by Sprague (Jenkin gives 
.324) for the amount of copper in milli- 
grams carried over in one second by a 
current of one Weber. Before making 
the test, the current was passed through 
the voltameter for some time, in a direc- 
tion opposite to that in which it was 
passed during the test, to insure that 
the copper carried over during the test 
was copper that had been deposited be- 
fore, otherwise energy may be lost in sep- 
arating the copper from the positive plate. 

SECOND METHOD. 

In detennining the electrical energy by 
the second method, a calorimeter was used 
which consisted of a cylindrical vessel of 
galvanized iron encased in a wooden jacket, 
and so supported as to leave an air space 
of about ^ an inch on all sides between 
the calorimeter and the jacket. This pre- 
vented any great conduction of heat from 



56 

the calorimeter to external objects ; still 
some heat must be wasted in heating the 
calorimeter and the surface it rests upon. 
To determine the amount of heat thus 
wasted 55 lbs of water was put in the cal- 
orimeter, and its temperature carefully de- 
termined it was 19.85°C. A large pail of 
water was then heated to 54.3°C, and 18J 
lbs. were poured into the calorimeter. This 
made the weight of water in the calorime- 
ter about "the same as was used in the 
test, and the same part of the calorimeter 
was heated in each case, the final tem- 
perature of the water being 28.50°C, the 
range of temperature used in the test was 
included in this range. The heat con- 
tained" in the water poured into the cal- 
orimeter may be represented by 18.75 X 
26.2=491.25. Of this 55x8.65=475.75 
went to raise the temperature of the water 
in the calorimeter, and the remainder 155 
must have been imparted to the calorime- 
ter. As the range of temperature in the 
calorimeter was 8.65°, 1.78 of these units 
were required to raise the temperature l c , 
or the same amount of heat was used in 



57 

heating the calorimeter as would be re- 
required to raise 1.78 lbs. of water through 
the same range of temperature ; therefore 
the proper correction may be applied by 
adding 1.78 lbs. to the weight of water in 
the calorimeter. 

To measure the heating effect of the 
current, a coil of copper wire was put into 
the calorimeter, the resistance of which 
was exactly .1 T V Ohm, at 74° F. The chief 
source of error in a calorimeter test of 
this kind is the tendency of the current to 
pass from one part of the wire to another 
through the water, instead of passing 
through the wire. This in itself is not a 
source of error if we measure the resist- 
ance of the coil in the water, but in so 
passing, it may carry metal from one part 
of the wire to another, and the energy so 
used cannot be calculated, and is lost ; to 
obviate this difficulty distilled water was 
used, the resistance of which is much 
higher than ordinary water. The resistance 
of the coil measured in the water did not 
differ perceptibly from its resistance in the 
air, and at the close of the test no evidence 



of copper having been carried from one 
part to the other was discernable. To de- 
termine the range of temperature dming 
the test, a Fahrenheit thermometer was 
used that was graduated to fifths of de- 
grees, but the graduation was so plain 
that twentieths of a degree could easily be 
read. In order to be certain that the tem- 
perature of the water was uniform 
throughout a pump was placed in the 
center of the calorimeter, which consisted 
simply of a copper tube about If" in di- 
ameter, its bottom was h' r above the bot- 

of the calorimeter and contained a 
valve opening downward ; the piston also 
carried a valve opening downward. The 

r in the calorimeter covered the top of 
the tube, and by this means the water 

taken from the surface when it is 
warmest, and carried to the bottom, where 

/oldest. The cumulation thus obtained 

very pe: I shown by some ink 

drops put in the pump barrel. 

THIED METHOD. 

In determining the electrical energy by 
the third method, the electro-motive force 



59 

was measured between the binding posts 
of the generator, by means of a Thomson 
high-resistance galvanometer. As a stand- 
ard of electro-motive force, Latimer Clark 
cells were used, four of which were made 
ujd new for the purpose. These agreed 
with each other very closely, and in using 
them they were connected in series, thus 
getting their combined effect, and averag- 
ing their errors. 

In using them they were allowed to 
charge a condenser, and the condenser 
was then discharged through the galvano- 
meter. 

The deflection produced is an accurate 
measure of the current flowing through 
the galvanometer and consequently of the 
charge held by the condenser, which de- 
pends upon the electro-motive f orr j of the 
terminals connected with the condenser. 
To connect the condenser alternately with 
the cells and the galvanometer, a simple 
switch was used by which the change could 
be made instantly. In making the test 
part of the condenser of .2 T 3 ^ microfarad 
capacity wire used and four standard cells 



60 



in series. The damping magnet of the 
galvanometer was then adjusted until the 
discharge of the condenser produced a de- 
flection of 291 divisions, as the electro- 
motive force of the cell is 1,456 volts and 
four in series were used, the deflection 

291 

corresponding to one volt was — — - — T 

1.456X4 

= 50. The instrument being standarized 

in this way, the liability to error was very 

small ; in use, however, T 9 F of the current 

was shunted from the galvanometer, only 

allowing T ^ to pass through, thus getting 

five deflections to a volt. 

The ends of all wires dipping into mer- 
cury were amalgamated with mercurous 
nitrate, which made the connections very 
perfect. 

In measuring the resistances of the 
armature and of the armature and leaders, 
the 'Wheatstone's bridge was used, and 
Thomson's reflecting galvanometer in 
place of the small galvanometer usually 
employed. The resistance of the armature 
mains and leaders was between .17 and 
.18 Ohm. When the bridge indicated .17 



/ 61 

the galvanometer showed a deflection of 
29.5 divisions ; when it indicated .18 the 
galvanometer showed an opposite deflec- 
tion of 45. From this we get the resist- 
ance of the armature mains and leaders, 
.17395 Ohm. 

The main alone measured .14460, leav- 
ing for the resistance of the armature and 
leaders to the binding parts .029 Ohm. 

Leading wires being clamped on the 
commutator the resistance measured in 
several positions was .16207. These 
leaders measured .14604, leaving for the 
resistance of the armature alone .016 
Ohm. 

The resistance of the field magnet coils 
was 37. Ohms. 

TEST BY VOLTAMETER. 

Before making the test the generator 
was run for some time to allow the circuit 
to heat up, and the resistance of the line 
measured from time to time until it was 
found to remain constant. The voltameter 
was then introduced into the circuit and 
allowed to remain fifteen minutes. 



During this time the speed of the dyna- 
mometer was detennined for ten mm 
and the average - mpated 

The deflection of the pendulum was ob- 
served every three minutes and the aver- 
age taken, although the variation was only 
one degree. At the end of the test the circuit 
broken and the resistance again 
measured, and it was found not to have 
changed perceptibly. 

The plates were then removed, washed 
in water, then in alcohol, and dried in a 
gentle heat. They were then weighed 
carefully. 

DATA OBTAINED FROM THE TEST 

Weight of copper gained by negative 

plates =24.465 m. g. 
Time of test = 15 minutes. 
TV eight gained per second == 27,183 m. g. 
Average speed of dynamometer = 1 

rev. per nrin. 
Average deflection of pendulum = 42 w 
Resistance of iron wire = .76 Ohm. 
Resistance of iron wires and magnet coils 

in multiple are = .744 Ohm. 



63 

Total resistance of circuit — .7444-029 = 

.773 Ohm. 
Internal resistance of armature == .016 

Ohm. 

RESULTS OBTAINED FEOM DATA. 

27.183 



Value of current in webers - 

.o245o 

83.753. 

Electrical energy (83.753) 2 X .773 X 44.24 = 

239880.726 ft. lbs. per minute. 
Energy indicated by dynamometer 171.2 

X(sin42°=.67344)x 4505 X 6.2832 

= 290125.54 ft. lbs. per minute. 
Friction of dynamometer and generator 

290125.54X.135 = 39166.9479 ft. lbs. 

per minute. 
Energy used in turning armature in field 

of force 290125.54x855 = 250958.59 

ft. lbs. per minute. 
Friction of dynamometer alone =290125. 5 

X. 109=31623.68 ft. lbs. per minute. 
Energy actually applied to armature pulley 

290125.54 X. 891 = 258501.96 ft lbs. 

per min. 
Of the total electrical energy 239880.7 



64 
,016 



.773 
.744 



4965.189 appeared in the armature, 
X 239880.726=4647.39 in the 



.773x49.68 

magnet coils, and 230268.176 ft. lbs. per 

minute in the external circuit. 

The efficiency of the generator is the 
ratio of the energy required to turn the 
armature hi the magnetic field, to the 
total electrical energy developed =r 
239880.726 _ 
"250958.59 

The commercial efficiency is the ratio of 
the energy required to drive the machine 
(including friction) to the electrical energy 
which appears in the external circuit 

230268.169 _ 
= -258501.96 - 8608 - 

TEST BY MEANS OF THE CALORIMETER. 

As in the voltametric test the generator 
was first run until the circuit was thor- 
oughly heated, and the same care was 
taken to determine the speed and deflec- 
tion of the dynamometer. When the 
calorimeter was thrown into the circuit an 



65 

approximately equal resistance was thrown 
out so as not to change the total resist- 
ance too much. At the end of the test 
the resistance of the circuit was measured 
carefully as soon as the circuit was broken 
and before the wires became cooled. 

DATA OBTAINED FROM THIS TEST. 

Water in calorimeter = 77 lbs. 
Connection for waste heat =1.78 lbs. 
Range of temperature = 79°— 69.8° = 

9.2 C F. 
Specific heat for this range = 1.0015. 
Average speed of dynamometer =394 rev. 

per min. 
Average deflection of pendulum = 43° 24' 

(sin =.68709). ' 
Time of tests = 16 minutes. 
Resistance of iron wires and calorimeter 

coH = .68 Ohm. 
This and magnet coil in multiple arc = 

.667 Ohm. 
Total resistance of circuit .667 + .029 = 

.696. 
Resistance of calorimeter coil = .1 Ohm. 



m 



RESULTS OBTAINED FROM THESE DATA. 

Energy developed in calorimeter = 
78118xl.0015x9.2x772 =35()22897ftlbs 

16 
per minute. 

Total electrical energy 
35022.897 X 6.96 =■ 243759.36 ft. lbs. per 
minute. 

Energy indicated by dynamometer = 
171.2 x .68709 X 894 x 6.2832 

= 291201.46 ft. lbs. per min. 
Energy used in turning armature in 
field of force 
591201.46 X. 865-= 

251889.265 ft. lbs. per min. 
Energy actually applied to armature 
pulley 
591201.46 x .891 = 

259460.5 ft. lbs. per min. 
Of the electrical energy 

243759.36x^=5603.66 
.690 

appeared in the armature 

243759 - 86 ^669fLl= 4215 - 89 



67 

in the magnet coils; and 233939.81 ft. lbs. 

per minute appeared outside. 

243759363 „ nrr 
Efficacy ^ 251889265 ^967. 

„ 233939.81 

Commercial emciencv^-p— — 7,-— -- — .901. 

259460.5 

TEST BY MEASUREMENT OF THE ELECTRO- 
MOTIVE FORCE AND RESISTANCE. 

In this test the electro-motive force was 
measured between the binding posts of 
the generator, and the external resistance 
was measured between the same points." 

The deflection and speed of the dyna- 
mometer were measured at the same time, 
the electro-motive force was observed and 
the resistance was measured just before 
and after these observations and was the 
same in both cases. 

DATA OBTAINED FROM THIS TEST. 

Electro-motive force = 53 volts. 
Resistance of circuit (external) .64 Ohm. 
Resistance between binding posts .629. 
Average speed of dynamometer, 355 rev. 
per min. 



68 



Average deflection, 42° (nat.sine=. 66913). 
Total resistance of circuit, .658. 

RESULTS OBTAINED FROM THESE DATA. 

Energy developed in external circuit 

V^- X 44.24=197567.43 ft. lbs. per min. 
629 

Total electrical energy 

197567.43 x^ = 206673.0295 ft. lbs. per 
• b ^ y min. 



Energy in armature 

206673.029 X '^ = 5025.5. 

.boo 

Energy in magnet coils 

^Jx 44.24 = 3346.667 ft. lbs. per min. 

Energy in external circuit 198300.88 ft. 

lbs. per min. 
Energy indicated by dynamometer 
171.2 x .66913 x 355 X 62332= 

2553 + 9.04 ft. lbs. per min. 
Energy used in turning armature in field 

of force 
255519. 04 x. 865= 

221023.97 ft. lbs. per min. 
Energy actually applied to armature pulley 



69 



255519.04x.891 = 

227667.47 ft. lbs. per min. 

_, ffl . 206673.0295 

EfficienC ^ -22102^97- = ' 935 - 

. " ■ . 198300.88 orT 

Commercial efficiency = —^^-.87- 

Average efficiency, .951. 

Average commercial efficiency, .887. 

ECONOMY OF THE CONDUCTORS. 

The economy of the conductors which 
convey the electricity from the generator 
to the lamps may be considered under two 
heads : first, the efficiency of the material, 
second, the efficiency of its dimensions. 

The efficiency of any material is deter- 
mined by its price and conductivity as 
compared with other materials. The two 
materials most commonly used for con- 
ductors are copper and iron. The present 
price of copper is about seven times the 
price of iron and its conductivity is about 
six times as great ; thus the actual cost of 
a line of copper wire of a given conductiv- 
ity is one-sixth greater than iron wire 
of the same conductivity. Copper wire. 



70 

however, is muck more uniform than iron 
wire: it is free from cinder streaks that 
are so common to iron wire, and is much 
more pliable and less bulky, and therefore 
less difficult to handle. For electric-light 
mains, which have to be frequently tapped, 
copj)er wire seems to be {^referable to iron 
wire. 

2d. the efficiency of dimension-. 

This is determined by the cost of the 
conductor and the loss of energy in the 
conductor. As the energy developed in 
different parts of the circuit varies directly 
as the resistance of these parts, some 
energy must appeal* in the conductors. 
This energy appears as heat, and is lost. 

The most efficient dimensions of the 
conductors depend upon the amount of 
energy to be transmitted and the distance 
which it is to be transmitted. 

To secure maximum efficiency, there- 
fore, we would have to calculate the most 
efficient size under all conditions as to 
number of lamps and distances. Know- 
ing, however, the conditions most usually 



71 



J 



met in practice, we can determine that loss 
of energy in the conductors, which is 
usually most efficient, and expressing this 
loss as a percentage of the total energy 
transmitted, calculate the size of our con- 
ductors upon this basis by making the 
resistance of the conductors the same j 
percentage of the total resistance of the 
circuit, as the loss of energy allowed is of 
the total energy transmitted. 

Thus, when we wish to calculate the 
dimensions of our conductors necessary 
to convey the current to a given number 
of lamps a given distance, allowing a loss of 

— of the total energy, we must determine 

the resistance of our lamps and make the 

resistance of our conductors — part of 

n— 1 x 

the resistance of the lamps. 

Thus we see that the cost of the con- 
ductors necessary to carry the current for 
a given number of lamps a given distance 
varies inversely as the resistance of the 
lamps, and although we can make a high 
or a low resistance lamp of the same 



r 




L/Z-* 


*J^ 






l- 






t*+ 




\j-*~ 



72 



economy, it will cost less to convey the cur- 
rent to a given number of high-resistance 
lamps a given distance, than it will to con- 
vey the current to the same number of low 
resistance lamps the sante distance. 

ECONOMY OF THE LAMPS. 

The economy of the lamps is deter- 
mined by the energy consumed and the 
amount of light produced ; in determining 
the energy consumed in the lamps, the 
electro-motive force was measured between 
the terminals of the lamps, and also the re- 
sistance, and the energy determined in foot 

e 2 
pounds per minute by the formula^- 44.24. 

In measuring the electro-motive force the 
same arrangements were used as in de- 
termining the electro-motive force of the 
generator, but the damping magnet was 
adjusted to give three units of deflection 
to a volt instead of five. To measure the 
resistance of the lamps when burning, the 
current was divided into two parts, one 
part was passed through the lamp and the 
other through a variable resistance, when 



^ 



90° 



90° 



CURVE SHOWING ILLUMINATION OF EDISON'S LAMP IN A HORIZONTAL PLANE. 




CCRVE SHOWING ILLUMINATION OF EDISON'S LAMP IN A HORIZONTAL PLANE. 



73 



both were passed through a differential 
galvanometer, but in opposite directions ; 
when the current was the same in both 
branches, the needle of the galvanometer 
would indicate zero. As the electro-motive 
forces of the two branches were equal, 
their currents were equal, when _ their 
resistances were equal, so by altering 
the variable resistance until the needle 
came to zero, and measuring the variable 
resistance we thus determined the resist- 
ance of the lamp while it was burning. 
This variable resistance was measured each 
time before it cooled. 

As the light given out in a horizontal 
plane varies at different angles, the angle 
of average iUumination . was first deter- 
mined for the ^mp used, which was the 
Edison lamp. To determine this angle, 
the candle po^ r was measured every 10° 
through a quar t, and the candle power 
observed laid o^ on a suitable scale on 
lines radiated from a point. A curve was 
drawn through the points thus determined, 
and the four quadrants being made 
symmetrical, its area was determined and 



74 



a circle of equal area drawn about the 
point from which, the lines radiate. The 
points where this circle cut the curve de- 
termine the angle at which the candle power 
is the same that it would be if the light 
were evenly distributed. 

Having determined the angular position 
of these points with reference to the plane of 
the carbon, all measurements were made 
with the axis of the photometer in this angle. 

To insure that the lamp was in this 
position, it was twisted until the shadow 
of the carbon fell on the center of the disc 
and then turned through an angle of 65°, 
which the curve shows to be the proper 
angle. All measurements of lamps were 
made at the angle of equal illumination. 

In order to determine the economy of a 
lamp at different degrees of incandescence, 
an Edison lamp was measured at intensi- 
ties ranging from a dull red to 40 candle 
power, and the results plotted in a curve 
show a rapid rise in economy as the candle 
power increases. While the economy of 
a lamp increases with incandescence, its 
life shortens, but as I have had neither 







_ 






o 












Ol 






K> 






O 






to 






Ol 






CO 






O 






CO 






Ol 






F» 






O 






■** 






OI 


" 


• 


O 






Q. 
O 






-a 

CD 

"I 


j 





)TOE. 






75 

time nor opportunities for life tests, I 
cannot give data for life at various degrees 
of incandescence. 

Mr. Edison's standard of illumination 
has been 16 candle power, and his aim has 
been to produce a lamp that will give good 
economy and a reasonable life at that 
candle power. 

To determine the energy consumed by 
these lamps when burning at their normal 
candle power, five lamps, as made at pres- 
ent by Mr. Edison, were tested with the 
following results : 

TABLE SHOWING ENERGY CONSUMED BY EDISON 
LAMPS. 




Ohms. 



Foot-pounds 

of Electricity 

per minute. 



135.5 
142.5 
140.5 
148.5 
131.5 



3178-03 
3021-91 
3107-41 
2861-15 
3319-32 



Showing an average of 3,097 — 564 ft. 





1000 Ft 


lbs. of Electrioit 


y per mi 




4000 


5000 


6000 




























I 
























































! 
















o 










\l 


























\ 


\ 


























\ 












o 




















































o 














































V 






o 

(0 














































\ 




o 
p 




















































£ 


























4 



cm™ s =o™ a nun between economy and h^esoenoe. 



76 



lbs. of electricity per minute, or 10.65 
lamps per h. p. of electricity, giving 170 
candles per h. p. 

Mr. Edison gets 10.65 lamps per horse 
power of electricity, but as he allows a loss 
of 10c of the electrical energy used in the 
lamps upon the conductors, he gets 9.68 
lamps for each h. p. of electricity genera- 
ated. As the average commercial efficiency 
of this generator is .887, this gives him 
8.58 lamps per dynamometrical h. p. 

The report of the Board of Commis- 
sioners of the Millers' Exhibition, held in 
Cincinnati just one year ago, gives the re- 
sults of the trial of three modem steam 
engines. 

These results show an average for the 
three engines of .878 of the indicated 
power converted into useful work ; using 
this factor for the conversion of dyna- 
mometrical into indicated horse power, we 
find that Mr. Edison gets 7.62 lamps per 
indicated horse power. 



DYNAMO-ELECTRIC CURRENT, 

AND OX 

Certain Means to Improve Its 
Steadiness. 



By C. WILLIAM SIEMENS, D.C.L., F.R.S. 



From Philosophical Transactions of the Royal 
Society. 



Steadiness of the Electric Current, 



On the 14th of February, 1867, I com- 
municated a short paper to the Koyal 
Society, describing the accumulative or 
dynamo-electrical principle of action, the 
conception of which I attributed to my 
brother Dr. Werner Siemens. When the 
pajoer was read, another paper followed 
by Sir Charles Wheatstone (sent in on the 
24th February) also describing this princi- 
ple of action, thus showing that the same 
line of thought had occupied that eminent 
philosopher. 

In illustration of my paper I exhibited 
a machine of my design, embodying the 
accunmlative principle of action, which 
furnished abundant evidence of the power- 
ful nature of the current that could be 
thus produced. It consisted of two 
horseshoe electro magnets, between the 
poles of which a Siemens armature could 



80 

be made to rotate, the machine being' 
furnished with a handle or pulley for that 
purpose. A commutator was provided, 
by which the alternating currents set up 
in the rotating coil (after a first impulse 
had been given) were directed through 
the coils of the stationary electro magnets 
in a continuous manner, and proceeded 
thence outward to ignite a platinum wire 
of some 12" in length, or to perform other 
work. 

This machine, although the first of its 
kind, has done good service ever since its 
construction, having been found very effi- 
cacious in exciting powerful permanent 
magnets at the telegraph works of Siemens 
Brothers at Woolwich. 

Since 1867 the accumulative principle 
has been employed in the machines of 
different makers, and one form of dynamo- 
electric machine, that of M. Gramme, dif- 
fers very materially from the machine 
above referred to, and had met very 
deservedly with extensive recognition. 
M. Gramme embodied in his machine the 
principle of Professor Pacinottfs mag- 



81 

netic ling, which enabled him to produce 
powerful electric currents without much 
of the loss of energy caused in previous 
machines through the heating of the 
rotating armature. 

Another modification of the dynamo- 
electrical machine is one devised by Mr. 
Von Heftner Alteneck, an engineer and 
physicist employed under my brother 
Werner Siemens, at Berlin. This machine 
differs from that first submitted by myself 
in several important particulars. Instead 
of the Werner Siemens armature, Yon 
Heftner Alteneck adopted a rotating coil 
of iron wire wound with insulated copper 
wire in more than one direction, the 
several coils of wire being connected 
seriatim with the commutator, and 
through it, with the wire surrounding the 
soft iron bars, and with the electric lamp 
or other resistance on the outer circuit. 

The advantage claimed for this mode of 
construction is that all the wire for min g 
the rotating coil or helix is brought into 
the magnetic field, excepting only those 
portions crossing from side to side of the 



82 

coil ; and in order to reduce this unpro- 
ductive resistance to a minimum, the 
rotating coil or helix has been made com- 
paratively long, and the number of electro 
magnets has been increased generally to 
six or more. 

The principal advantage of the dynamo- 
electrical machine over all other current 
generators consists in its power of pro- 
ducing currents of great magnitude, and 
of an intensity up to 100 volts, with a 
small primary resistance, and therefore 
with a comparatively small expenditure of 
mechanical energy. It labors, on the 
other hand, under the disadvantage that 
the power of the current depends, at a 
given velocity, upon the magnetic force 
developed in the electro magnets. This 
force depends upon the amount of current 
passing through the coils of the magnets, 
which in its turn is dependent in an 
inverse ratio upon the resistance in the 
outer circuit; If from some accidental 
cause the external resistance is increased, 
the electro-motive force of the machine, 
instead of rising to overcome the obstruc- 



83 

tion, diminishes, and thus aggravates the 
resulting disturbance. If, on the other 
hand, the resistance of the outer circuit 
diminishes, as in the case when the car- 
bons of an electric regulator touch one 
another, the electro magnets are immedi- 
ately excited to a maximum, and the 
electro-motive force of the machine is 
increased. The power absorbed and its 
equivalent, the heat generated in the cir- 
cuit, is equal to the square of the electro- 
motive force divided by the resistance; 
hence the work demanded from the engine 
will be greatly increased, the machine may 
be dangerously overheated, and powerful 
sparks may injure the commutator. It is 
chiefly owing to this instability of the 
dynamo-electric current that its applica- 
tion to electric illumination has been 
retarded, and that magneto-electric ma- 
chines and machines producing alternating* 
currents have been again used, although 
they are inferior to the dynamo machine 
in the current energy produced for a given 
expenditure of mechanical energy. 



84 

The properties of dynamo-electric ma- 
chines have been examined by several 
observers. Messrs. Houston and Thom- 
son (Franklin Institute) compared the 
efficiency of the Gramme, Brush, and 
Wallace Farmer machines. Dr. Hopkin- 
son (Institution of Mechanical Engineers, 
25th April, 1879) examined a medium- 
sized Siemens machine, determined its 
efficiency, and expressed the electro- 
motive force as a function of the current. 
Herm Mayer and Anerbach ( Wiedemanns* 
Annalen, November, 1879) and M. Mas- 
cart have experimented on the Gramme 
machine, and Mr. Schwendler on both 
Gramme and Siemens machines. 

The radical defect of the dynamo ma- 
chine of ordinary construction, may be 
inferred from the results of these experi- 
ments. The remedy has, however, been 
in our hands from the time of the first 
announcement of the principle of these 
machines before the Royal Society, when 
Sir Charles Wheatstone pointed out that "a 
very remarkable increase of all the effects, 



85 

accompanied by a diminution in the re- 
sistance of the machine, is observed when 
a cross wire is placed so as to divert a 
great portion of the current from the 
electro magnet." 

Some of the constructors of dynamo 
machines, namely: Mr. Ladd in this 
country, and Mr. Brush in the United 
States of America, have taken advantage of 
this suggestion, the latter with the avowed 
object in view of obviating spontaneous 
changes of polarity in effecting electro 
precipitation of metals, and without per- 
haj)s having realized all of the advantages 
of which this mode of action is capable ; 
others have refrained from doing so on 
account of difficulties resulting, as I shall 
endeavor to show, from an insufficient 
examination into some important physical 
conditions that require attention in order 
to realize economical results. 

An ordinary medium-sized Siemens- 
Alteneck dynamo- electrical machine has 
wound on its rotating helix insulated cop- 
per wire of 2.5 m.m. diameter in 24 sec- 
tions, representing a resistance of .4014 



8o 

S. XL* The four electro-magnet coils 
connected seriatim are composed of cop- 
per wire of 5.5 m.m. diameter, presenting 
a total resistance of 0.3065 S. U. 

If (as has frequently been done) the 
wires of this machine were to be con- 
nected as suggested in Sir Charles Wheat- 
stone's original paper, thus making the 
outer circuit hot continuous with but 
parallel to the coil circuit, and if the outer 
circuit had a resistance of one unit, it 
would follow that the total resistance 
to the current set up by the rotation of 
the armature would be reduced from 

.4 + .8 + 1=1.7 to .4 + ^^ = 0.61 unit, 
1 + .o 



* The resistance coils used in these experiments were 
graduated according to the mercury system introduced 
by Dr. Werner Siemens, and adopted by the Tele- 
graphic Convention at Vienna in 1868. The B. A. unit 
was determined in 1874 by Kohlrausch to be 1.0493 
S. XL, or combined with Lorenz's value of the S. U. 
afterwards adopted, 0.9797X109 C.G. S. units— as much 
as 2 per cent, below its ascribed theoretical value. 
Later determinations by H. F. Weber (Phil. Mag., 
March, 1878) makes the S. U. to be equal to 0.955X109 
C. G. S. units, and thus the Ohm to be 0.2 per cent, 
higher than its ascribed value ; if this latter value is 
used, the numerical results must be correspondingly 
altered. 



87 

causing a great increase of current, the 
major portion (in the proportion of 10 to 
4) would flow through the electro mag- 
nets, thus causing a great increase of 
heating effect. The resistance of the field 
magnet must therefore be greatly in- 
creased, but if it were attempted to 
increase that resistance simply by reduc- 
ing the diameter of the wire, and increas- 
ing the number of convolutions until the 
same thickness of coil was obtained, the 
magnetic excitement and with it the 
electro-motive force of the current pro- 
duced at a given velocity of rotation 
would suffer a material decrease. The 
current flowing through the helix coil 
would moreover have to divide itself, and 
in order to reach the same limit in the 
outer circuit its intensity in the helix coil 
would have to be increased, causing it to 
heat more readily than before. It was 
necessary, therefore, to raise the effect of 
the magnet current to the same level as 
before with as small a proportion of the 
helix current as possible, in order to leave 
a maximum proportion of the current for 



88 

the outer circuit. In order to effect this, 
the magnet bars had to be increased in 
length, and placed further apart so as to 
provide room for coils of greatly increased 
weight and dimensions ; at the same time 
the helix wire had to be increased in 
diameter to give room for the aggregate 
current, but in reality I found it advan- 
tageous to increase the diameter of the 
same in a much greater proportion. 

These general conditions having been 
determined by preliminary experiment, 
Mr. Lauckert, electrician engaged at my 
works, undertook a series of comparative 
experiments which are given in the 
appendix attached to this paper, and the 
results are given numerically and exhib- 
ited in curves. On examining the curves 
it will be remarked: 

1. That the electro-motive force instead 
of diminishing with increased resistance, 
increases at first rapidly, then more slow- 
ly towards an asymptote. 

2. That the current in the outer circuit 
is actually greater for a unit and a half 
resistance than for one unit. 



89 

3. With an external resistance of one 
unit, which is about equivalent to an 
electric arc when 30 or 40 webers are 
passing through it, 2.44 horse power is 
expended, of which 1.29 horse power is 
usefully employed ; an efficiency of 53 per 
cent, as compared with 45 per cent, in the 
case of the ordinary dynamo machine. 

4. That the maximum energy which can 
be demanded from the engine is 2.6 horse 
power, so that but a small margin of 
power is needed to suffice for the greatest 
possible requirement. 

5. That the maximum energy which can 
be injuriously transferred into heat in the 
machine itself is 1.3 horse power, so that 
there is no fear here of destroying the 
insulation of the helix by excessive heat- 
ing. 

6. That the maximum current is ap- 
proximately that which would be habitu- 
ally used, and which the commutator and 
collecting brushes are quite capable of 
transmitting. 

Hence I conclude that the new machine 
will give a steadier light than the old one, 



90 



with greater average economy of power, 
that it will be less liable to derangement, 
and may be driven without variation of 
speed by a smaller engine ; also that the 
new machine is free from the objection of 
having its currents reversed when used 
for the purpose of electro deposition. 

The same peculiarity also enables me 
to effect an important simplification of the 
.regulator to work electric lamps, to dis- 
; pense with all wheel and clock-work in 
the arrangement, as shown in Fig. 1. The 
two carbons, being pushed onward by 
gravity or spring power, are checked 
laterally by a pointed metallic abutment, 
situated at such a distance from the arc 
itself that the heat is only just sufficient 
to cause the gradual wasting away of the 
carbon in contact with atmospheric air. 
The carbon holders are connected with 
the iron core of a solenoid coil, of a re- 
sistance equal to about fifty times that of 
the arc, the ends of which coil are con- 
nected with the two electrodes respect- 
ively. The weight of the core, which has 



91 

to be maintained in suspension by the 
attractive force produced by the current, 
determines the distance between the 
electrodes, and hence the electric resist- 
ance of the arc. The result is that the 
length of the arc is regulated automati- 
cally so as to maintain a uniform resist- 
ance, signifying a uniform development of 
light. 

APPENDIX. 

The measurements of the electric cur- 
rents were made with an electro dyna- 
mometer, the movable part of which con- 
sisted of a single turn of 4 m.m. wire, and 
the stationary coil of nine turns of the 
same. 

To be able to reduce the electrical 
measurements into absolute power devel- 
oped, it was in the first place necessary to 
determine the constant of the instrument 
in use. This was done in the following 
manner: Five copper plates of about 
11" X 8" were connected as shown hi the 
sketch. 



92 



These were carefully weighed and im- 
mersed i in a solution of sulphate of cop- 
per. The machine was previously started, 
the time of immersion carefully noted, and 
the readings of the current taken every 
half minute. The plates were so arranged 
that the current entering at a and leaving 
at z deposited the copper on both sides of 
the plate at z. After a certain time the 
plates were taken out, quickly rinsed in 
water, and dried in sawdust. The plates 
were then carefully weighed again and 
the deposit calculated per degree reading 
on the instrument per second of time. 
Six independent measurements were taken 
with currents varying from 20 to 40 
webers, and gave a mean of .000779 
gramme of copper per second per degree 
reading. The differences of these meas- 
urements from the mean varied from 0.21 



93 

per cent, to 6.6 per cent., the mean of the 
differences being 1.98 per cent. 

According to F. Kohlrausch (Pogg. 
Ann., Bd. cxlix., 1873) the quantity of 
silver deposited by the C. G. S. unit of 
electricity is 0.011363 gramme, and since 
the quantities vary as the equivalents of 
the metals deposited, we have 

.011363 X68.5 =a003840 



216 
gramme of copper. 

One weber being -^ C. G. S. unit, we 
have to divide by 10 the quantity of cop- 
per deposited by a current of one weber 
in one second, that is .000334 gramme, 
and dividing .000779 by .000334 we get 
2.23323 webers for a degree reading of 
our instrument. 

To be able to compare the machines 
having the new winding (i. e., the wire on 
the electro magnets connected parallel 
with the outer circuit) with the ordinary 
machines, it was necessary to experiment 
on the relation existing between the power 
expended and the current produced with 



94 



different resistances in circuit and differ- 
ent speeds. 

• A medium dynamo machine with 24 
part commutator was used, the helix being 
wound with 336 convolutions of 2.5 m. m. 
wire, having a resistance of .4014 S. U. 
when measured in the machine. The 
electro magnets were wound with four 
layers of 5.5 m.m. wire, each having 32 
convolutions, and therefore the four bob- 
bin a. total of 512 convolutions with a 
resistant of, .3065 S. U. 

The accompanying Tables Nos. 5, 6, 7, 
8, and 9 give the details of the experi- 
ments made, which are shown graphically 
in the diagrams similarily numbered. The 
current in webers was simply calculated 
by multiplying the square root of the 
reading on the electro dynamometer with 
the constant of the instrument, i. e., 
2.3323. 

To be able to calculate the electro- 
motive force from the current in webers 
and resistance in Siemens' units, it was 
necessary to convert the S. U. into C.G.S. 
units by multiplying the same by .9337 X 



95 

10 9 . (This figure is given by Lorenz, 
Pogg. Aim., Bd. cxlix., 1873.) By again 
multiplying this resistance into the cur- 
rent we get, according to Ohm's law, the 
electro-motive force in C. G. S. units, and 
by dividing by 10 8 we get the E. M. F. in 
volts. 

I have further calculated the total 
amount of work developed in the follow- 
ing manner : 

Work done =E X C X t, or, which is the 
same, C 2 xRX?, where E is E. M. F; C, 
current; R, resistance; t, time. 

From these calculations t is eliminated 
as it occurs in all the equations. 

1 volt^lO 8 C. G. S. units. 

1 weber^Y 1 ^- C. G. S. unit of current. 

1 HP=7.46xl0 9 C. G. S. units. 

Therefore 

1 voltxl weber _ 10 8 xl0- 1 _ 1 
1HP~ "~7.46xl0 9 ~~746 

and if we multiply the E. M. F. in volts 
by the current in webers, and divide by 
746, we have the actual work developed 
in horse power. 



96 

To find the actual work clone in the 
outside resistance we use the fomiula 
C 2 xK of course having to reduce the 
resistance R into absolute C. G. S. units 
by multiplying by .9337x10 . 

The machine with the new winding had 
a helix with 24 part commutator wound 
with 312 convolutions of 2.8 m.m. wire. 

The electro-magnets being lengthened 
by 2" to take bobbins 10J", instead of 
8^'' as on the ordinary machines. I had 
three sets of bobbins made, and had the 
same wound with different sizes of wire, 
viz. ; 2.5 m.m.. 2.8 m.m.. and 3 m.m.. hav- 
ing a respective resistance of 11.26. 7.563. 
and 4.46 S. U. 

The accompanying Tables Xos. 1. 2, 3, 
and 4 show the experiments made with 
this machine with electro-magnets of 
11.26 S. T. resistance; Nos. 10, 11, 12, 
and 13 with electro-magnets of 7.563 S.U.; 
and Xos. 14 and 15 with electro-magnets 
of 4.46 S. U. The helix in all cases hav- 
ing- been wound with 2.8 m.m. wire with 
a resistance of .234 S. 17. when measured 
in the machine. 



97 

The Tables marked 5, 6, 7, 8, and 9 re- 
fer to the dynamo machine wound in the 
ordinary way. 

The Tables marked 16. 17. 18, 19, 20, 
21, 22, and 23 show the results obtained 
with a machine having a helix wound with 
288 convolutions of 3 m.m. wire and a 
resistance of .173 S. units. The electro- 
magnets, as before, had a resistance of 
11.26, 7.563, and 447 S. U. 



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Electric Lighting 



PARIS EXHIBITION. 



By WILLIAM HENRY PREECE, F. R. S. 



Prom the "Journal of the Society of Arts/" 



■3 & *r -5 % 



Electric Lighting at the Paris 
Exhibition. 



The recent International Exhibition of 
Electricity in Paris makes an epoch in the 
history of the practical applications of 
that science to Arts, Manufactures, and 
Commerce. I purpose now to refer only 
to its application to artificial illumina- 
tion ; but there are many other branches 
fully deserving examination and discus- 
sion by this Society. It was, however, as 
an exhibition of electric lighting that it 
was principally attractive, and those who 
saw it for the first time will never forget 
the vivid impression that the great blaze 
of splendor produced upon their minds 
on entering the building. There never 
can be anything like it again, for as wis 
dom grows with exj^erience, so no man- 
ager of any future Exhibition is likely to 
repeat that terrific melange of lights that 
flooded the interior of the Palais de Tin- 



126 

dustrie with great brilliancy, but with an 
impracticable and impossible means of 
comparing and judging the relative mer- 
its of different systems. 

For instance, at the foith coming Exhi- 
bition at the Crystal Palace, the build- 
ing—splendidly adapted for the purpose 
— will be divided into sections, each sec- 
tion being lit by one, and only one sys- 
tem. But at Paris, Pelion was piled 
upon Ossa ; the British Section, for in- 
stance, received rays from at least a 
dozen different sources. To estimate the 
value of a Siemens lamp you had to 
eliminate the disturbing influence of a 
blazing Crompton ; and to admire the 
star-like Jaspar arc, you had to run the 
gauntlet of a flock of Swans. The fret- 
ful Jamin, or the fitful Jablochkoff, was 
masked by the steady Gulcher or the 
brilliant Serrin. In the galleries, how- 
ever, it was different. Here, different 
dalles were illuminated by different sys- 
tems ; a small theatre was lit by the 
Werderman lamp, and a picture gallery 
most effectively shown up by the Lampe 



127 

Soleil; a buffet was softly and brightly 
lit up with the Swan lamp, while Mi\ 
Edison's numerous exhibits, in his own 
salo?is, were as visible by night as by 
day, thanks to his own beautiful lamp. 

It is not my intention to examine, serl- 
atim, the various machines, lamps, and 
modes of illumination shown. With 
most of them, you are already familiar. 
But I purpose to select what appeared to 
me to be novelties, and what seemed 
worthy of being brought to your notice, 
as steps in advance. 

On the night of August 29th, there 
were in operation 277 arc lamps, 116 can- 
dles, 44 arc incandescent lamps, 1,500 
incandescent lamps, or a total of 1,837 
electric lights in all, at the Paris Exhi- 
bition. Towards the end of the period 
during which the show was opened, this 
number was very largely increased, and I 
have little doubt that the number reached 
2,500 in the beginning of November. 
Now this army of lamps required power 
to convert the energy stored up in coal 
into energy of motion: dynamo -ma- 



chines to convert the energy of motion 
into electrical energy ; conductors to 
3 energy to the point 
to be illuminated : lamps to convert the 
electric energy into energy of heat, and 
therefore of light. 

xhibition of engines and ma- 
chic E ve. although our 
English manufacturers failed to do what 
they might have done had they thought 
as highly of the Exhibition at first as they 
afterwards. Many of our man' 

^icuous by their absence, 
■nlyext- to by Met 

f Lincoln, who showed 
eight of their well-known engines, with a 
total _ " and I have 

D to behV :heir su 

imply repaid them for their en 
Mr. Brotherhood made a small 
show of his well-known three-cylinder 
engines and - Wallis & 

:oke. sent one of their semi-fixed 

la-engines, with their pretty and ef- 

inor for adjusting the speed 

while in motion — uniformity in speed be- 



129 

ing an essential criterion of an electric 
light engine. The foreigners, for a won- 
der, far outshone the British in the mag- 
nitude of their displays. 

One of the most valuable exhibits was 
made by Messrs. Thomson, Sterne & Co., 
who showed a new gas engine on a new 
principle, which attracted a great deal of 
attention. Gas is destined to play a most 
important role in the future of electric 
lighting. Its function is that of a heat- 
generator. The energy of the coal exists 
in gas in a form which can develop more 
light, when converted into the form of 
electricity, by the current, than in the 
form of heat by combustion. Gas en- 
gines have a very high theoretical effi- 
ciency, and they are free from the dangers 
of boilers, the neglect of stokers, or the 
waste of energy in chimneys. 

Gas engines on the il Otto " principle, 
from half horse power to 50 -horse power, 
were very extensively exhibited by 
France, but the machine of Thomson, 
Sterne & Co. (Clerk's patent) excelled 
them all in lightness, compactness, regu- 



130 

larity, and safety. One of these engines 
may now be seen at work at the Smoke 
Abatement Exhibition at South Kensing- 
ton, and several have been ordered -for 
private houses. As an adjunct to the 
gas engine, Mr. Dowson exhibited an in- 
teresting and valuable process of making 
cheap gas for motor purposes. Prof. 
Ayrton reported that in a series of trials 
made with a 3 J H. P. (nominal) "Otto" 
engine, driven by the Dowson gas, one 
H. P. (indicated) was obtained per hour 
by the consumption of gas derived from 
1.46 lbs. of coal. For larger engines he 
anticipated a consumption of only 1.2 
lbs. per indicated horse power per hour. 
You will have a paper during the Session 
by Mr. Dowson himself, describing his 
mode of manufacture. When perhaps 6 
lbs. of coal per horse power per hour are 
consumed in the present electric-light 
steam-engines, you can form some idea of 
the economy to be effected by cheap gas. 
Dynamo - machines — machines which 
convert the energy of motion into electri- 
cal energy, through the medium of mag- 



131 

netism — were exhibited in abundance, of 
all kinds and forms, from the original 
apparatus of Faraday, made with his own 
hands, to Mr. Edison's latest develop- 
ment of this wonderful source of electric 
currents. There are two kinds of ma- 
chines — the one producing currents from 
fixed and permanent steel magnets, the 
other from electro-magnets, excited by 
the currents which they themselves gene- 
rate. Each kind is also sub-divided into 
two others, in one of which continuous 
currents are produced, flowing in one di- 
rection, called the continuous current 
nine; and in the other alternate cur- 
rents, called the alternate current ma- 
chine, where the current rapidly reverses 
and changes its direction. The produc- 
tion of currents by these machines is due 
to the smrple fact discovered by Faraday, 
that if a conductor, such as a copper 
wire, be moved rapidly through a magnet- 
ized space, or a magnetic field, as it is 
called, this conductor is electrified so 
that, if its two ends be connected, a cur- 
rent flows. The intensity of this current 



132 

depends, first, on the intensity of the 
magnetism present, on the velocity with 
which the conductor moves through the 
field, and on the direction with which it 
cuts the lines of magnetic force which 
permeate the magnetic field. The mag- 
neto-electric kind — the manufacture and 
invention of Bi. de Meritens — are very 
much approved of by our Trinity House 
for lighthouse purposes, and a very fine 
display of them was made by Bf. de Men- 
tens, who seemed to live in the Exhibi- 
tion, for he was always there, and who 
never seemed to tire of giving his clear 
and able descriptions. He exhibited al- 
ternate and continuous current machines. 
and he richly deserved the gold medal 
that was accorded to him. The exhibition 
of dynamo -machines was rendered very 
interesting by the exhibition of an early 
machine of Elias, of Haarlem, of 1842. 
and of Pacinotti's machines of 1861. The 
former was shown in the Dutch Section. 
and the latter in the Italian. Here we 
have the germs of all the present ma- 
chines, and by whatever name a machine 



133 

may be known, it can be traced back to 
these original types. The Pacinotti ap- 
paratus has been very greatly improved 
by Gramme, and by Siemens — forms well 
known to every one — but it has received 
its greatest development in the Edison 
machine, which was one of the wonders 
of the Exhibition. As this was one of the 
greatest novelties, I must briefly describe 
it. In the first place, I must point out 
that the machine is larger than any one 
that has ever been made before. It 
weighs, with engine and bed plates, 20 
tons, and it can produce a current of 
electricity of nearly 900 amperes.* As 
the largest machine of the Gramme type 
weighs scarcely one ton, and produces a 
current of but 93 amperes, the difference 
becomes striking. Now, Mr. Edison has 
struck out three new paths, first — in the 
bulk and form of his electro-magnets, 
second — in the size and construction of 
his armature, and third — in the low re- 
sistance of his revolving coil. By the 



♦The largest Brush machine weighs two tons, and 
absorbs 40-horse power. 



134 

first, he secures an intense and concen- 
trated magnetic field, by the second he 
secures a high cutting velocity for the 
moving conductor through this field, and 
by the third, he secures a very powerful 
current to be distributed among a great 
number of lamps with the least possible 
waste of energy. The long and bulky 
coils, 8 feet long, which constitute his 
electro-magnet, have excited the surprise 
of many electricians, but there is no doubt 
that he has arrived at this form after 
many careful practical experiments, sup- 
ported by the mathematical investiga- 
tions of Professor Kowland — a very high 
authority — and that the result is to ob- 
tain an intense field in a large space, 
with the least absorption of electrical en- 
ergy in the coils. With 350 revolutions 
per minute he is able to produce an elec- 
tro-motive force of 110 volts, which an 
ordinary Gramme machine can only at- 
tain with over 1,000 revolutions per min- 
ute. His field-magnets are wound with 
copper wire, which have a resistance of 
30 ohms, and which are connected as a 



135 

shunt to the main circuit, as was origi 
nally done by Wheatstone, and is now 
followed by Dr. Siemens and Sir William 
Thomson. The armature is not wound 
with wire, but is constructed with solid 
bars of copper f in. by ^ in. section, and 
3^ feet long, which are well insulated 
from each other, and are most ingeniously 
connected at their ends by copper discs, 
so that all the bars, of which there are 
138, form one continuous circuit, whose 
total resistance is only 0.008 of an ohm. 
The diameter of the armature is 28 inches. 
The core of the armature is made up of 
1,700 thin iron discs insulated from each 
other by paper, and well clamped into a 
solid mass by bolts. This is done to 
avoid the heating effects due to so-called 
Foucault currents induced in the metal 
and absorbing or wasting energy. The 
iron core of the armature becomes thus 
magnetized, and it concentrates the field 
to the space through which the conductor 
moves, as is done in Siemens' and other 
machines. 

There are two great troubles in exist- 



136 

ing machines, want of uniformity in their 
motion and the slipping of belts. The 
former is met by governors, and the lat- 
ter by direct gearing. Steadiness of mo- 
tion is most essential, otherwise we have 
that painful throbbing of the light that is 
so irritating to the eyes. Mr. Edison 
connects his armature direct to his steam 
motor, which is a high-pressure engine of 
the Allen-Porter type, governed by an 
ingenious centrifugal regulator, and ro 
tating very uniformly at 350 revolutions 
per minute, without any multiplying gear 
whatever. When the machine is giving 
out its maximum commercial effect it ab- 
sorbes 125-horse power, the external re- 
sistance should be 16 times that of the 
armature, the electro -motive force 110 
volts, and the current consequently 860 
amperes. It is not safe to exceed this 
limit, for the armature then becomes un- 
duly heated. A special blower is added 
to direct cold air on the armature to keep 
down the heat, when the work of the 
machine approaches its limit. The brush 
is a special feature of the machine. The 



137 

absence of sparking was very striking. 
Mr. Edison coats his brush and commu- 
tator with an amalgam of copper, which 
diminishes the electrical resistance of 
contact, reduces the heat, and prevents 
sparking. 

Those who are interested in this ma- 
chine — and every one should be, for it is 
a decided step in advance — will soon have 
an opportunity of seeing it at work at 57, 
High Holborn. 

There was a very interesting form of 
Gramme machine shown, which was main- 
tained at a velocity of 2,400 revolutions 
per minute, and was said to generate an 
electromotive force of 2,000 volts. It 
maintained 60 Jamin candles alight. But 
one of the best and most compact forms 
of Gramme was that shown by the Brit- 
ish Electric Light Company, designed by 
their engineer, and made for them by 
Messrs. Emerson, in Stockport. 

The display of lamps was the display 
of the building. There were very few 
novelties among arc lamps. An arc lamp 
consists of two sticks or rods of carbon, 



138 

which are kept apart a small fraction of 
an inch while the current flows through 
them, but which comes together when 
the current ceases. Across the interval 
separating them there is a steady flow of 
electricity, accompanied by a slow con- 
sumption of the carbon of each. rod. 
This flow of electricity produces high 
temperature, and intense incandescence 
and combustion of the carbon particles. 
This is the arc. One lamp differs from 
another only in the way in which the car- 
bons are moved forward as they consume, 
so as to maintain the resistance equal 
and the light steady. Among arc lamps, 
that which signaled itself out among all 
its compeers, for steadiness and bril- 
liancy, was the Jaspar lamp, exhibited in 
the Belgian Section ; but it had the dis- 
advantage of absorbing all the energy of 
one machine. Among those that admit- 
ted of having a number on one section, 
perhaps the simplest in its construction 
was the Gulch er, exhibited in the Aus- 
trian Section ; but the most effective and 
original was the "Pilsen" lamp, the in- 



139 

vention of Messrs. Piette & Krisik. It is 
called the "Pilsen '? lamp, from the place 
of its birth, and from the want of eupho- 
niousness in the names of its inventors. 
It was exhibited in the Austrian Section, 
and also in the British Section, by Mr. 
Fyfe. The carbons are kept apart by a 
sucking coil when the current flows ; they 
are regulated by a second sucking coil 
worked on a shunt. The peculiarity of 
the lamp consists principally in the shape 
of the core that controls the carbon — it 
is wedge-shaped at each end ; in action is 
wonderfully regular, and almost perfect. 
Six lamps were worked in one circuit by 
a Schuckert machine. 

The Lampe Soleil, which holds an in- 
termediate position between arc and in- 
candescent lamps, made a very effective 
display in the picture gallery, where there 
were 20 lamps in 10 lanterns. It is to 
be seen in London lighting up the Pano- 
rama in Westminster. It is a fixed, 
steady, durable lamp, giving a soft yel- 
lowish light, which is due to the fact that 
the arc maintains in incandescence a 



140 

highly refractory substance like marble, 
between the two ends at the carbon. It 
is a very simple lamp, for it involves no 
mechanism whatever; but it is said to 
absorb a great deal of power, though I 
have seen no reliable figures of its per- 
formance. Its consumption of carbon is 
remarkably small. It is worked by an 
alternate current machine, which, like 
most of these machines, made a most un- 
pleasant hum. 

Carre made a very fine display of car- 
bons for arc lights, for the manufacture 
of which he is so famous, in which the 
regularity of form, of structure, and of 
composition, is said to be absolute ; but 
it is very questionable whether this is 
really the case in practice, for the irregu- 
larity of the arc lights is chiefly due to 
impurities and irregularities in the car- 
bon. Moreover, the very vast discrep- 
ancies that are found in the photometric 
measurements of the same lamp at differ- 
ent times, or by different persons, may 
be due to the irregularities in the struc- 
ture of the artificial carbon rods. 



141 

No one can deny that the Jablockhoff 
candle has done good service in the 
cause of electric lighting; but I am 
afraid that the Exhibition in Paris has 
sounded the knell of all forms of candle, 
as well as those of the Werderman type. 
The rising favorite is the incandescent 
lamp, pure and simple. The display 
made by Mr. Swan in the buffet, in the 
Congress Hall, and in the Pavilion at the 
Post-office, was brill ant and effective. 
The light was soft, uniform, and yellow. 
The incandescent light is totally free 
from those bright rays that are so in- 
jurious to the eyes, so uncomplimentary 
to the complexion, and so irritating to 
the worker, if they are accompanied with 
the least unsteadiness. It is so readily 
under control ; it requires • no skilled 
labor to replace it or attend to it ; it can 
be fixed anywhere ; it can be worked 
into the fixtures and decorations of a 
room, and it does not damage them, as 
gas and oil do. Incandescent lamps can 
be worked by either continuous or alter- 
nate current machines. In fact, the 



142 

chief lesson of the Paris Exhibition is 
this, that the arc light is specially suited 
for external illumination, and that incan- 
descent lamps are eminently adapted for 
internal and for domestic illumination. 
This lesson has been carried into prac- 
tice at the Savoy Theatre, where nothing 
can be more effective or more efficient 
than the illumination of the auditorium. 
One can breathe pure air, feel cool, and 
can sit out a play without incurring a 
headache. There were several incandes- 
cent lamps shown at Paris besides those 
of Mr. Swan, notably those of Maxim 
and Lane-Fox ; but that which possessed 
the greatest novelty, and was decidedly 
the most efficient, was that of Mr. 
Edison. The distinctive character of 
the Edison lamp is the remarkable uni- 
formity of its texture and light- giving 
power. The lamp consists of a fine fila- 
ment of carbon inserted as a part of the 
electric circuit in a glass globe, which 
has been exhausted of air to the utmost 
limit of workshop skill. A. fine, uniform 
quality of Japanese bamboo has been se- 



143 

lected as that which gives the finest tila 
ment for carbonizing. The bamboo is 
cut by special machinery into the re- 
quired dimensions, and inserted in a 
mould, which is placed in a furnace, and 
raised to a very high temperature, and 
from which the filament comes out 
shaped and carbonized. Naturally grown 
vegetable fiber has been found to give a 
morennr^m texture than any artifici- 
ally-formed carbon. The ends are cut 
flat, and squeezed inside copper clamps, 
which are then welded together by 
electro -plating. The copper clamps being 
soldered to platinum-loads that are sealed 
through the glass, and are connected to 
the conductors. Perfect sealing is ob- 
tained by flattening the mass of the tube, 
through which the fine platinum wires 
pass into a solid bar, so as to well fuse 
the wires and glass together. It is a 
fortunate thing for the permanence of 
the incandescent lamp that the co-efficient 
of expansion, due to heat, of glass and 
platinum is practically the same. 

The normal lamp consists of a filament 



144 

6 inches long, which gives a resistance 
of 240 ohms when cold, and, when per- 
meated by a current of 0.8 ampere, gives 
a light equivalent to 16 sperm candles. 
The half lamp is constructed with a car- 
bon filament of just half the length and 
half the resistance, and gives eight 
candles. Other lamps are made with two 
and four horse-shoe filaments, so as to 
increase the light-giving power. The 
features of carbon, which render it so 
highly adapted for incandescence, are its 
electrical resistance, its high refractory 
character, and its stability. The illumi- 
nation of a filament and its durability are 
functions of the current that passes ; the 
more intense the current the higher the 
temperature, and therefore the brighter 
the light and the shorter its life. At a 
temperature of about 1,000° carbon be- 
comes red, at 2,000° it is white, and the 
higher the temperature the whiter it 
gets, until it fuses. A current of 0.8 of 
an ampere maintains an Edison filament 
at about 2,000°, when it gives a light of 
16 candles, and it lasts on an average 



145 

1,000 hours. A stronger current will 
give a much better light, but the carbon 
will not last so long. If it were possible 
to find a form of carbon, or any other 
materia], which would be so refractory 
that we could transmit through it much 
stronger currents, the incandescent lamp 
would rival the arc lamp in brilliancy and 
power. 

The destruction of the carbon filament 
in incandescent lamps is due to what is 
called the Crookes' effect, a very slow 
transference of carbon, in a molecular 
shower, from the one heel to the other 
heel of the horseshoe, until a breakdown 
takes place at the former point. The 
better the vacuum the slower this effect. 
Alternate c urren t m achin es are s aid to 
len gthe n the life of the carbons, by 
equalizing the distribution of molecules 
on each heel, but they do so at the ex- 
pense of efficiency. 

Many devices were shown for measur- 
ing the quantity of electricity consumed 
in any place by electric lamps ; but that 
adopted by Mr. Edison is sufficiently 



146 

simple and accurate for all practical pur- 
poses. A glass cell contains two copper 
plates immersed in a solution of sulphate 
of copper. A definite proportion (0.001) 
of the current that passes through the 
house passes also through this cell, and 
removes copper from one plate and de 
posits copper on one plate. The weight 
of copper deposited is an exact measure 
of the current used. There are two 
such cells — the one in charge of the con- 
sumer and the other of the supplier. 
They thus check each other. 

Various plans were shown in different 
parts of the Exhibition to diffuse the 
light, but the most effective was that in 
Shite 15, where a Jaspar lamp filled the 
room with a shadowless light, by throw- 
ing a light on to a white screen above 
the lamp, whence it was scattered. The 
lamp itself was invisible. This plan is 
not novel. It was suggested by the 
Duke of Sutherland, and has been adopted 
by Mr. Schwendler in India. 

The proper distribution of light is a 
problem that remains to be solved. It is 



147 

argued that an arc is so much superior 
to an incandescent light, that one-horse 
povVer in the former gives you ten times 
more light than in the latter. This is 
true ; but. on the other hand, to obtain a 
subdued light sufficient for your purpose, 
you must either put the arc lamp far 
away or tone it down by shades, and 
therefore waste it ; whereas an incandes- 
cent lamp can be toned down, by regu- 
lating the current, to any color you like, 
and it can be fixed just where it is 
wanted. • One-horse power will give you 
1,500 candies in an arc. and only 160 
candles in 10 incandescent lamps; but 
these 10 lamps can be so distributed 
about your space to be lit. as to illumin- 
ate your surface or objects with a bet- 
ter light than the arc. 

Curiously enough nothing whatever 
was done in Paris to improve the illumin- 
ation of streets. The Avenue de TOpera, 
the first street practically lighted by 
electricity, still remains as it was in 1878; 
but prior to the opening of the Exhibi- 
tion, a portion of the Boulevard des 



148 

Italiens was lit up by four De Mersanne 
lamps, suspended high up, at wide inter- 
vals, over the center of the road. The 
effect was very fine, but the lamps were 
very bad. This is the true way of illu- 
minating streets, and it is to be regretted 
that such an experiment is not tried in 
London. Street illumination in England 
by electricity up to the present time is, 
as a rule, a questionable success. 

The question remains for discussion : 
Has the electric light been brought with- 
in the region of practical domestics ? I 
have no hesitation in saying that it has ; 
but whether it can be brought into eco- 
nomical contrast with gas, experience 
alone will show. Several houses are al- 
ready illuminated by its agency ; others 
are in hand, my own amongst the num- 
ber ; and when we next meet to consider^ 
this subject, I may be able to answer the 
question with actual facts. 

One word as regards the danger of 
electric lighting. There is no use blink- 
ing our eyes to the fact that electricity 
can be a dangerous servant in the hands 



149 

of the careless and ignorant ; in the hands 
of the skilled it has less danger than gas, 
or even oil. The installation of the wires 
must be controlled by experience and 
knowledge. I have more than once called 
attention to this fact, and my warnings 
have been received with abuse; but in 
Paris there were no less than five incipi- 
ent fires, from the wires coming in con- 
tact with each other, in the Exhibition 
building. The Times correspondent in 
Vienna implies that the frightful disaster 
to the Ring Theatre was due to this 
cause. The instances in New York are 
so numerous that the Board of Fire un- 
derwriters have issued the following 
rules : — 

u L Wires to have 50 per cent, excess 
of conductivity above the amount calcu- 
lated as necessary for the number of 
lights to be supplied by the wire. 

" 2. Wires to be thoroughly insulated 
and doubly coated with some approved 
material. 

" 3. All wires to be securely fastened 
by some approved non-conducting fasten- 



150 

ing, and to be placed at least 2^ inches 
for incus light, and 8 inches for 

arc lights, from each other, and 8 inches 
from all other wires and from all n> 
or other conducting substance, and to be 
placed in a manner to be thoroughly and 

b. When it- 
becomes necessary to carry wires thr< 
partitions and floors, they must be 
cured against contact with metal or other 
conducting substance in a manner ap- 
proved by the inspector of the Board. 
"4:. All arc lights must be protec 

at the bottom. 
t<> effectually prevent sparks or particles 
of the carbons from falling from the 
lam} show windows, mills, and 

- materials of* 
an inflammable nature, chimneys with 
spark arresters shall be placed at the 
of the globe. Open lights positively 
prohibited. The conducting framework 
of chandeliers must be insulated 
covered the same as wi: 

• ". "Wher^ nducted 

into a buiJding (from s< rher than 



151 

the building in which it is used) a shut- 
off must be placed at the point of en- 
trance to each building, and the supply 
turned off when the lights are not in use. 
Applications for permission to use elec- 
tric lights must be accompanied with 
a statement of the number and kind of 
lamps to be used, the estimate of some 
known electrician of the quantity of 
electricity required, and a sample of the 
wire (at least three feet in length) to be 
used, with a certificate of said electrician 
of the carrying capacity of said wire. 
The applications should also state where 
the electricity is to be generated, whether 
the connection will have metallic or 
ground circuit, and, as far as possible, 
give full details of the manner in which 
it is proposed to equij) the building." 

These rules are very simple, and are 
necessarily carried out by every qualified 
electrician, but an additional security is 
obtained by Mr. Edison, by inserting in 
every branch wire a u safety catch," 
which is a short piece of lead wire that 
instantly melts if the strength of the cur- 



♦ 152 

rent exceeds a certain value, and thus 
ruptures the circuit, stopping the flow of 
electricity, and producing safety. 

The completeness of Mr. Edison's ex- 
hibit was certainly the most noteworthy 
object in the exhibition. Nothing seems 
to have been forgotten, no detail missed. 
There we saw not only the boilers, 
engine, and dynamo machine, but the 
pipes to contain the conductors ; the 
conductors themselves, heavy and mass- 
ive, for Mr. Edison recognizes the waste 
of energy that must occur in small con- 
ductors, the insulation, the fixtures, the 
brackets, the safety catches, the lamps, 
devices to avoid the effects of expansion 
and contraction through changes of tem- 
perature, meters to measure the current 
used, regulators to control the consump- 
tion of fuel. In a properly regulated 
system there ought to be no waste of 
fuel. The engine driver has an indicator 
which shows him exactly what current is 
going out, and he has simply to regulate 
his firing by this indicator. Moreover, 
by the use of a rheostat, he is also able 



153 

to regulate the outgoing current so that 
lie is able to maintain a perfect ratio 
between the fuel consumed and the light 
evolved. 

The question that determines the size 
and insulation of conductors is a com- 
mercial one, % and is regulated by the 
relative economy of waste of energy or 
interest on capital expended. If an ex- 
penditure of £100 per mile saves you 
£10 a year in fuel, it is clearly better to 
expend £100 on your conductor. If, on 
the other hand, it would save you only 
£2 a year, it is better to utilize your 
capital elsewhere. Every inch of con- 
ductor means waste of energy; the 
shorter and heavier it is the less the 
waste ; but as some waste is imperative, 
it is simply a matter of calculation to de- 
termine which shall be wasted least, 
capital or fuel. 

The system is self -regulating, if the 
electromotive force is kept constant, and 
the resistance of the lamps be uniform. 
We have the dynamo machine at one end 
of the circuit, and a lamp at the other. 



154 

The circuit is complete ; a small current 
flows, which is determined by the resist- 
ance of the lamp alone, if the main con- 
ductors are made sufficiently large to 
neglect their resistance. Additions and 
subtractions of lamps only vary the re- 
sistance, and, therefore, the current. 
Turning off one lamp does not interfere 
with the rest. The limit of the number 
of lamps inserted is determined by their 
resistance and by the heating of the • 
armature ; hence the value of high re- 
sistance in the lamps, and low resistance 
in the armature of the dynamo machine. 
Every lamp induces, as it were, its own 
current. We have not a store of elec- 
tricity which has to be subdivided, but 
we generate our energy as we want it. 
This is the promising feature of the sys- 
tem. It is a principle of multiplication, 
rather than of sub-division, and leads one 
to anticipate economy in its working. 
Mr. Edison's system has been worked 
out in detail, with a thoroughness and 
a mastery of the subject that can extract 
nothing but eulogy from his bitterest 



155 

opponents. Many unkind things have 
been said of Mr. Edison and his prom- 
ises ; perhaps no one has been severer 
in this direction than myself. It is some 
gratification for me to be able to an- 
nounce my belief that he has at last 
solved the problem that he set himself to 
solve, and to be able to describe to the 
Society the way in which he has solved 
it. 

It may be taken as a rule, that any 
system dependent on the exercise of ab- 
normal energy is certain sooner or later 
to break down ; we all of us hate personal 
supervision, and personal supervision at 
home is a species of abnormal energy. 
This is the great secret of the success of 
gas. It is the cause of the slow progress 
of the arc light ; but it is because the in- 
candescent light promises to rival gas in 
this respect, that such a future is open to 
it. 

The awards at the Paris Exhibition 
were liberally bestowed by the jury, per- 
haps too much so ; but matters were 
hurried up towards the end, owing to 



156 

political difficulties, and the conclusions 
were necessarily hasty. No proper 
measurements c were made by 

any jury, but a committee, presided over 
by M. Tresi n fcimed^tc 

nue the work, and there is no doubt 
ble results will be ob- 
tain^ - of the jury to pro- 
cure reliable measurements has been very 
generally met by the exhibitors, I had 
->es of being able to give you 
the i :o-night, but the reports are 
not yet ccmplete. 

We shall all, very seen, have a repe- 
d on a different scale, and in a dif- 
ferent way. at the Crystal Palace, and I 
have little doubt that, in its way, the 
Crystal Palace Exhibition will be as fine 
and as interesting as that of Paris. 



DISCUSSION. 

_e Chairman said he could not oper. 
the discussion better than by callirjg en 
Mr. Johnson, the representative of Mr. 
.Edison. 



157 

Mr. Johnson said he did not know that 
he could supplement what had been so 
well said by Mr. Preece, so as to add to 
the interest of the subject, but he should 
be ready to explain anything which had 
been left unexplained, and he would also 
illustrate, further, the use of some of the 
apparatus. He wished, however, to say 
that Mr. Edison's system was not merely 
a system of electric lighting ; but the 
novelty of his. system lay in this, that 
he contemplated the manufacture of 
electricity on a large scale at a central 
station, and its universal distribution 
throughout the entire area of the city 
where it was established, to be used by 
uneducated or unscientific people, with- 
out the supervision of trained experts in 
the employment of the company. They 
proposed to put the electric light into 
houses in such a simplified form, and 
with such provisions, as to render super- 
vision entirely unnecessary ; to bring the 
lamps within the care of ordinary house 
servants, no matter how ignorant they 
might be ; and in such a way that no 



158 

damage or waste was possible. The 
electricity thus converted into light might 
also be converted into power, by means of 
an electro motor ; and it might be utilized 
in a variety of ways, such as for ringing 
bells, &c. The annoyance of maintaining 
a battery, as well as its expense, had 
hitherto proved a bar to its general use, 
but when electricity could be supplied 
and paid for only as used, to be shown 
by a meter, an immense deal of work, 
such as driving sewing machines, &c, 
would be done by it There had been a 
good deal of talk about a regulator, and 
Mr. Preece had shown that one might be 
made to maintain an even pressure 
throughout an entire district lighted 
from one station, no matter how many 
lamps were lighted by it. They pre- 
ferred to have such a regulator with 
personal supervision, just as gas compan- 
ies regulated the pressure on their mains 
as required, rather than employing any 
automatic device, which was liable to get 
out of order. [Mr. Johnson here sjiowed 
how the amount of current could be in- 



159 

creased or diminished at will, so that 
when fewer lights were in use, the quan- 
tity would be diminished accordingly.] 
The man in charge of the central station 
would regulate the current by a sample 
lamp kept alight there. He had been 
asked whether the replacement of the 
lamps, when used up, was expensive or 
difficult. In answer to that, he might 
say that in New York, where they were 
making arrangements to light up a 
central district of a mile square, they 
j)roposed to supply every consumer with 
all the lamps he might use, free from 
cost, simply charging the cost of the 
lamp in the current supplied and paid 
for on his meter. The first cost of the 
lamps was very small to them, and they 
therefore preferred supplying them to 
subjecting the consumer to the annoy- 
ance of having to purchase them. [Mr. 
Johnson here unscrewed a lamp, and 
attached another, to show the readiness 
with which a change could be effected.] 
A question had also been asked him, 
whether a single light could be raised or 



160 

lowered ; and there was a lamp made in 
which this was provided for, but it was 
more expensive and complicated, and was 
not recommended. There were very few 
cases where such would be required, be- 
cause you need not leave a light on as in 
the case of gas, in order to light up when 
required, as you only had to turn it on. 
and it lit itself. 

Sir Henry Tyler, K.C.B., moved a vote 
of thanks to Mr. Preece, but remarked 
that the paper hardly answered to the 
title, inasmuch as it was mainly devoted 
to an explanation of Mr. Edison's lamps, 
and he thought there might have been a 
little more time bestowed upon other 
lamps. He was far from wishing to 
disparage the Edison lamp, and no one 
had more sympathy than he had with 
American inventors; but he would sug- 
gest that the title of the paper should be 
altered when printed. 

Mr. E. Crompton said he had been 
much interested in the paper, but he 
must concur to some extent in Sir H. 
Tyler s remarks. Many, if not all, of the 



161 

merits of the Edison lamp were common 
to other incandescent lamps. He, there- 
fore, thought Mr. Swan and Mr. Lane-Fox 
ought not to be passed over in silence, 
or Mr. Maxim, the other great American 
inventor. Mr. Preece had been rather 
hard on the arc systems, which he said 
had made comparatively little progress ; 
but in reply to that, he would ask the 
meeting to look at the length and breadth 
of England, where, since that time last 
year, there had been from 900 to 1,000 
installations of the electric light, which, 
with the exception of 30 or 40, were all 
on the arc system, and, with very few 
exceptions, they were all working most 
successfully. The incandescent systems 
were working equally successfully, but 
the whole system was an infant compared 
to the arc, and had not yet been worked 
on a sufficiently large scale to judge of 
its merits. It had hitherto been placed 
in circumstances not best suited for it. 
The lighting of the Savoy Theater was a 
great success, in his opinion, but no one 
could say that that vast open space could 



162 

not be lit more satisfactorily with arc 
lights, if good ones, and properly man- 
aged. The arc light hitherto had had to 
struggle with the great difficulty of get- 
ting homogeneous carbons ; but new 
manufacturers were setting to work, and 
he believed the trade of making these 
carbons would soon become one of the 
great industries of the country. It re- 
quired nothing but the enormous demand, 
now springing up, to produce splendid 
carbons, w T hich would give a perfectly 
satisfactory light. 

Mr. J. N. Shoolbred said he had noth- 
ing to add to Mr. Preece's descript on of 
the Paris Exhibition, but he thought his 
remarks as to the future sphere of the arc 
light and the incandescent light respect- 
ively should be somewhat modified. He 
did not think the arc light need be con- 
fined merely to large open spaces. It 
was a question of the enormous differ- 
ence of mechanical energy ; and a case 
which recently came under his notice 
would illustrate this. It was the interior 
of a building considerably larger than 



163 

that hall, which it was found would re- 
quire about 6-horse power to light it by 
the arc system, whilst on the incandes- 
cent system it would 9 have taken nearly 
40-horse power, and from 170 to 200 
lights. With regard to the experiments 
shown that evening, he must fully concur 
in what had been said as to the beautifully 
steady character of the lights, but at the 
same time it was only fair that due 
credit should be given to other inventors. 
Mr. Hugh Clements remarked that Mr. 
Edison had evidently gone beyond any 
one else, up to the present time, in the 
manufacture of his 20- ton machine at any 
rate. Mr. Preece, of course, could not 
enter fully into the details of all the 
lights ; but he understood him now to 
withdraw a statement he had made on a 
former occasion, that it was impossible 
for private houses to be lit up by elec- 
tricity from a central station. There 
was evident proof that this was being 
done in New York, and he hoped the 
time would soon come when they would 
see the same thing in London. 



164 

Captain Verney, R.N., said it might be 
interesting to the meeting to hear the 
opinion of one of the general public, en- 
tirely unconnected with any electrical in- 
terest. He had visited the Paris Exhi- 
bition twenty or thirty times, and had 
been many times in both the Edison and 
Swan rooms. He must say that he came 
away with the impression that on the 
whole the Lane-Fox was the most satis- 
factory exhibit. He was also much im- 
pressed with the beauty of the Lampe 
Soleil, which Mr. Preece had alluded to, 
but not described very minutely. One 
of its great beauties was, that you could 
introduce other substances as a bridge 
between the carbons, and thus vary the 
color and quality of the light. The light 
was exceedingly soft and agreeable, be- 
ing generally overhead, and it seemed to 
him an enormous advantage to be able to 
introduce marble, magnesium, or some 
other substance, and so tone the light a^ 
to be suitable to the place to be illumin- 
ated. He hoped those who had the 
management of the Exhibition at Crystal 



165 

Palace, would enable the general public 
to gather from it more information than 
was available at Paris. There they were 
furnished with an incomprehensible cata- 
logue, referring to numbers which did 
not exist, and to rooms which could not 
be found. It was a most perplexing 
thing for any one with the average amount 
of intelligence and energy, to learn any- 
thing from the Paris Exhibition. 

Mr. Lascelles Scott did not propose 
to launch upon the vexed question with 
which the discussion opened, further 
than to suggest that, as Mr. Preece had 
on former occasions spoken rather ad- 
versely to Mr. Edison, he felt constrained 
now, with more information, to do him 
full justice. He thought the time was 
hardly arrived to pronounce definitely 
that the arc light was only suitable for 
large open areas, and that the incandes- 
cent system was best for internal use, or 
vice versa, because in all probability, in 
a few years, such an opinion would be 
very much modified. Judging from his 
own small experience, he desired to place 



166 

on record his opinion that probably the 
domestic lamp of the future would be 
one in which the prominent features 
of both systems were combined, which 
would illuminate a room alternately, or 
almost at the same time, by either a small 
arc or an incandescent lamp. There was 
already a system which professed to do 
something of the kind. 

The Chairman said he thought that 
the last speaker had really given the an- 
swer to the objection raised by Sir H. 
Tyler, by referring to Mr. Preece's de- 
sire to restore the equilibrium of the 
balance, which, on a former occasion, had 
been unduly depressed on one side. 
Passing from this matter and going to 
the real subject of the paper, they had 
before them a remarkable example of the 
incandescent light, and he thought they 
must all agree that if this light could be 
introduced into houses, in the same way 
as gas, and at- no greater, or a very little 
greater, expense, it would be forthwith 
adopted. A lamp which did not vitiate 
the atmosphere in the least, which gave 



167 

off but a small amount of heat, which 
was capable of being absolutely extin- 
guished, and then renewed again in a 
moment, was one which all would wil- 
lingly take instead of a gas lamp, which 
certainly did pollute the air, heated it in- 
conveniently, and if there were too much 
pressure, or the burner were out of or- 
der, smoked and spoiled the furniture 
and pictures. Und^ these circumstances 
he thought it could not be doubted that 
if they could all, by a mere word, change 
their gas fittings and lights to such as 
they saw there, that word would be ut- 
tered ; but then came the question, how 
near were they to that being practically 
and commercially possible ? He believed 
they were very near to it. It had been 
said, and truly, of the electric light, as 
one of Dickens' characters said of the 
steam engine, that it was yet in its in- 
fancy. Sometimes infants grew up well, 
and became a pleasure to their parents : 
sometimes they grew up ill : but he be- 
lieved this infant would turn out a credit 
to its parents, and that they would soon 



168 

have the electric light laid on in the man- 
ner which had been stated. The difficul- 
ties at present attendant on applying it 
to individual houses, were those con- 
nected with the motive power, a large 
question which he could not then fully 
go into: but" there was a system, some- 
what inaccurately called "storage of elec- 
tricity," by which there might be brought 
into any house a dumber of boxes, not 
storing electricity, but each containing 
an apparatus which had, by the agency 
of electricity, been put into a condition 
competent to develop electricity in an 
absolutely regular manner, a most need- 
ful quality for the satisfactory produc- 
tion of the incandescent light, although 
he must say no want of steadiness was 
observable from the working of the en- 
gine that evening. You could, there- 
fore, by the aid of these boxes, practi- 
cally have electricity brought into your 
house, as you had gazogenes, ready 
charged, or as he remembered many 
years Lgo, portable gas was carted to 
houses in this city. Unless there were 



169 

some such system as that, persons who 
wanted to use the electric light had to 
resort to a motor of some kind, and there 
was the choice between steam engines 
and gas engines. A large steam engine 
at present was more economical than a 
gas engine, but on the other hand, it re- 
quired a more skilled attendant. To 
work a gas engine, you had to do little 
more than turn a tap, and to oil occa- 
sionally ; the stoker and engine driver 
were really at the gas works. The man- 
ager there supplied a regular flow and 
jiressure of gas, and in that way the la- 
bor of attendance to each engine was re- 
duced to a minimum. In the case of 
small engines, this non-necessity for 
skilled attendance reduced the cost prac- 
tically far below that of a steam engine. 
For that reason, he believed, that the in- 
dividual lighting of houses would be 
done by gas engines, and that if you took 
the gas with which your house was 
lighted, and applied it to work an engine, 
you would obtain a greater amount of 
light from incandescent lamps than by 



170 

burning the gas direct. The calculation: 
had been gone into very carefully, and 
were it not for the cost of replacing the 
. lamps, it was quite clear that even now 
economy was considerably on the side of 
electricity. He was glad to hear from 
Mr. Johnson that in America the compa- 
ny preferred to include the replacement 
of the lamps in the fixed charge for the 
electricity ; but that could hardly be done 
where each man had to produce his own 
electric current. A thousand hours was 
stated to be the average life of these 
lamps, some being much above and others 
much below the average. The other day 
a committee, of which he was a member, 
did not feel it safe to calculate the aver- 
age at more than 500 hours, and then 
putting the cost of renewal at 5s., it 
turned out that that, added to the fuel, 
made the electric lighting rather dearer 
than gas, and they had deferred the con- 
sideration of the matter for a few weeks 
to obtain further information. But if 
electricity could be laid on to houses, no 
doubt the problem would be, to a large 



171 

extent, solved. One of the great difficul- 
ties was in the meter, but they had bad 
one of a very ingenious and apparently 
efficient character exhibited that evening, 
and that might render practicable the 
establishment of a company for laying 
on electricity like gas or water, charging 
the consumer only for what he used. 
With regard to another point which had 
been considered a great difficulty — the 
division of the current — Mr. Preece said 
it was not really a divided current, but 
that each lamp induced its own current. 
That did not seem to him a very happy 
mode of expressing it, and he would en- 
deavor to explain it in another way. Each 
of the lamps they would see, was situated 
between two parallel wires, from which 
went two small wires, which were attach- 
ed to the filament of carbon in the lamp. 
Now, if instead of electricity they sup- 
posed water were being used, and that 
the wires represented the pipes, and one 
pipe contained a pressure of water, while 
the other acted as a return pipe, there 
being no connection between the two ex- 



172 

cept by small pipes, represented by the 
wires going to each lamp, as long as only 
one of these small pipes was opened, the 
quantity which would pass would be only 
as much as could be transmitted by the 
one small connecting pipe ; if two were 
opened, there would be double the quan- 
tity, and so on. Assuming for the mo- 
ment that none of the pipes were open, 
then having' once established a pressure 
of water, it required no energy to main- 
tain it, if there were no leaks. You could 
bring the pressure np to a 100 lbs. on 
the square inch, and if there were no 
leak it would continue for ever ; but if 
you established a connection between the 
pressure pipe and the return pipe, and 
allowed one gallon per minute to flow 
away, you must exert as much energy as 
would supply one gallon per minute un- 
der a pressure of 100 lbs. Similarly, if 
you established a connection between one 
wire and another, which allowed a given 
amount of electricity to pass, you must 
employ us much energy as would develop 
electricity equal in quantity and ten- 



173 

sion to that which had passed away: 
if you had ten wires connected, 
you must develop ten times as much 
energy. So that it was not in truth 
a sub- division of the current, but was al- 
lowing the current to now, and regulat- 
ing the amount of power to be put on 
accordingly. It would be easy to ascer- 
tain, by an indicator at the central sta- 
tion, what the demands were, and deter- 
mine what should be the amount of 
pressure, as it were, in the conductors, 
and the number of horse power required 
to be developed in the engine, in order 
to supply the pressure. Mr. Johnson 
gave as an illustration the governor at a 
gas works, which controlled the pressure 
in the mains, and which had to be varied, 
from time to time, according to the draft 
upon them. At this time of the year, 
probably at half-past three, there would 
be a rise of pressure of so many tenths, 
another rise at four, again at half-past 
four, and so on until you got to the time 
when the theaters and shops were all 
using gas ; and then came the maximum, 



174 

which would be maintained until ten, 
when there would be a slight reduction, 
and a further reduction at midnight, 
when the uniform night pressure would 
come on and be maintained until about 
six ; and then perhaps the day pressure 
would come on. and be maintained until 
the afternoon. A gas manager plotted 
this out on a sheet of paper which was 
affixed to the instrument, and this drew 
on the same sheet of paper, a trace show- 
ing the amounts and the durations of 
the pressure actually given, by the gov- 
ernors, so that, according to the way in 
which the pencil followed the lines al- 
ready laid down, the manager could 
judge of how his directions had been 
carried out. Thus, by looking at the pa- 
per, you could tell if there had been a 
foggy day. If the day pressure provided 
for was say \ f , and the implement showed 
there had been f J, you would know that 
there had been a fog, that the paper had 
had to be disregarded, and extra press- 
ure put on. As he understood, provi- 
sion would be made in the same way for 



175 

i 



ncreasing the electric current when re- 
quired. With respect to the arc and in. 
candescent lights, they would all agree 
that no one could dogmatize on what 
would be the light of the future, the 
whole matter being, as yet, too much in 
the trial stage ; but, at present, he thought 
all would prefer the incandescent light 
for domestic illumination. It was ad- 
mitted that the arc light w^as much more 
economical, perhaps 10 to 1 ? Mr. Shool- 
bred said 8 to 1. Then Mr. Preece ob- 
jected to the arc light being placed high 
up ; but it was shown conclusively to the 
committee that sat on the lighting of 
Liverpool, that there really was no loss 
by placing the light high up. It was 
true the. effect of the light diminished 
with the square of the distance, and that, 
therefore, a light a hundred feet up 
would give fcnly one - hundredth, part 
of the intensity of light that would 
be given by the same light if it were 
ten feet up; but, assuming an equal 
diverging angle for the really effective 
rays, it would, on the other hand, 






176 

light a hundred times the area. The 
only difference, probably, would be the 
want of penetrating power in ease of 
fogs. 

The vote of thanks having been passed 
unanimously, 

Mr. Preece, in reply, said it appeared 
that his sins had been rather of omission 
than commission, and this would be fur- 
ther explained by the opening paragraphs 
of his paper. It must also be remem- 
bered that that was the third or fourth 
time he had read a paper before the So. 
ciety on electric lighting, and the sixth 
or seventh time he had spoken on the 
subject, and he had not, of course, again 
gone over ground he had already trod- 
den. It would not be true to entitle his 
paper a description of the Edison light, 
as other matters were treated; but it 
was evident that what he had said abou 
it, and "what had been seen by the audi- 
ence, had produced a very deep impres- 
sion on their minds. 



vf 



H 589. 



